Pop the last item off of an array without using built in the array.pop() function
I'm trying to complete a problem that involves removing the last item of an array without using the built-in .pop function. Here is the full problem...
Write a function which accepts an array.
The function should remove the last value in the array and return the value removed or undefined if the array is empty.
Do not use the built in Array.pop() function!
Example:
var arr = [1, 2, 3, 4];
pop(arr); // 4
I figured out how to grab the last number with the following code but this obviously doesn't solve the problem.
function pop (array){
for (i=array.length-1; i>array.length-2; i--){
array = array[i]
} return array
}
pop ([1,2,3,4])Thanks in advance!
javascript arrays
edited Nov 23 '18 at 20:17
Scott Marcus
38.8k52036
asked Nov 23 '18 at 20:11
Marsden MarsMarsden Mars
254
add a comment |
I'm trying to complete a problem that involves removing the last item of an array without using the built-in .pop function. Here is the full problem...
Write a function which accepts an array.
The function should remove the last value in the array and return the value removed or undefined if the array is empty.
Do not use the built in Array.pop() function!
Example:
var arr = [1, 2, 3, 4];
pop(arr); // 4
I figured out how to grab the last number with the following code but this obviously doesn't solve the problem.
function pop (array){
for (i=array.length-1; i>array.length-2; i--){
array = array[i]
} return array
}
pop ([1,2,3,4])Thanks in advance!
javascript arrays
edited Nov 23 '18 at 20:17
Scott Marcus
38.8k52036
asked Nov 23 '18 at 20:11
Marsden MarsMarsden Mars
254
1
Try withslice()... developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…
– LGSon
Nov 23 '18 at 20:12
simple,array.reverse().shift()then reverse it again..
– rlemon
Nov 23 '18 at 20:15
First check the array length. If it is zero, return undefined. Otherwise, save the last array element in a local variable (using length-1 to access it). Then decrement the length, and return that local variable.
– Michael Geary
Nov 23 '18 at 20:21
add a comment |
I'm trying to complete a problem that involves removing the last item of an array without using the built-in .pop function. Here is the full problem...
Write a function which accepts an array.
The function should remove the last value in the array and return the value removed or undefined if the array is empty.
Do not use the built in Array.pop() function!
Example:
var arr = [1, 2, 3, 4];
pop(arr); // 4
I figured out how to grab the last number with the following code but this obviously doesn't solve the problem.
function pop (array){
for (i=array.length-1; i>array.length-2; i--){
array = array[i]
} return array
}
pop ([1,2,3,4])Thanks in advance!
javascript arrays
edited Nov 23 '18 at 20:17
Scott Marcus
38.8k52036
asked Nov 23 '18 at 20:11
Marsden MarsMarsden Mars
254
I'm trying to complete a problem that involves removing the last item of an array without using the built-in .pop function. Here is the full problem...
Write a function which accepts an array.
The function should remove the last value in the array and return the value removed or undefined if the array is empty.
Do not use the built in Array.pop() function!
Example:
var arr = [1, 2, 3, 4];
pop(arr); // 4
I figured out how to grab the last number with the following code but this obviously doesn't solve the problem.
function pop (array){
for (i=array.length-1; i>array.length-2; i--){
array = array[i]
} return array
}
pop ([1,2,3,4])Thanks in advance!
function pop (array){
for (i=array.length-1; i>array.length-2; i--){
array = array[i]
} return array
}
pop ([1,2,3,4])function pop (array){
for (i=array.length-1; i>array.length-2; i--){
array = array[i]
} return array
}
pop ([1,2,3,4])javascript arrays
javascript arrays
edited Nov 23 '18 at 20:17
Scott Marcus
38.8k52036
asked Nov 23 '18 at 20:11
Marsden MarsMarsden Mars
254
edited Nov 23 '18 at 20:17
Scott Marcus
38.8k52036
asked Nov 23 '18 at 20:11
Marsden MarsMarsden Mars
254
edited Nov 23 '18 at 20:17
Scott Marcus
38.8k52036
edited Nov 23 '18 at 20:17
Scott Marcus
38.8k52036
edited Nov 23 '18 at 20:17
Scott Marcus
38.8k52036
38.8k52036
asked Nov 23 '18 at 20:11
Marsden MarsMarsden Mars
254
asked Nov 23 '18 at 20:11
Marsden MarsMarsden Mars
254
asked Nov 23 '18 at 20:11
Marsden MarsMarsden Mars
254
254
1
Try withslice()... developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…
– LGSon
Nov 23 '18 at 20:12
simple,array.reverse().shift()then reverse it again..
– rlemon
Nov 23 '18 at 20:15
First check the array length. If it is zero, return undefined. Otherwise, save the last array element in a local variable (using length-1 to access it). Then decrement the length, and return that local variable.
– Michael Geary
Nov 23 '18 at 20:21
add a comment |
1
Try withslice()... developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…
– LGSon
Nov 23 '18 at 20:12
simple,array.reverse().shift()then reverse it again..
– rlemon
Nov 23 '18 at 20:15
First check the array length. If it is zero, return undefined. Otherwise, save the last array element in a local variable (using length-1 to access it). Then decrement the length, and return that local variable.
– Michael Geary
Nov 23 '18 at 20:21
1
1
Try with
slice() ... developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…– LGSon
Nov 23 '18 at 20:12
Try with
slice() ... developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…– LGSon
Nov 23 '18 at 20:12
simple,
array.reverse().shift() then reverse it again..– rlemon
Nov 23 '18 at 20:15
simple,
array.reverse().shift() then reverse it again..– rlemon
Nov 23 '18 at 20:15
First check the array length. If it is zero, return undefined. Otherwise, save the last array element in a local variable (using length-1 to access it). Then decrement the length, and return that local variable.
– Michael Geary
Nov 23 '18 at 20:21
First check the array length. If it is zero, return undefined. Otherwise, save the last array element in a local variable (using length-1 to access it). Then decrement the length, and return that local variable.
– Michael Geary
Nov 23 '18 at 20:21
add a comment |
6 Answers
6
active
oldest
votes
EDIT: This includes a null and empty check.
var array = [1, 2, 3, 4, 5];
function pop(array) {
return array && array.splice(-1)[0]
}
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(array);answered Nov 23 '18 at 20:15
MariusMarius
867
This doesn't meet the requirements
– Wayne Phipps
Nov 23 '18 at 20:23
2
Yep, now you're returning an array. :)
– Mark Meyer
Nov 23 '18 at 20:27
1
Haha @MarkMeyer , none of us are reading. Updated.
– Marius
Nov 23 '18 at 20:30
1
This worked, thanks so much!
– Marsden Mars
Nov 23 '18 at 20:32
1
@Marius Try repeating theconsole.log(pop(array))at the end of your snippet a few times, and then add aconsole.log(array)at the end, and see what it logs. Does the code do what the problem specification requires?
– Michael Geary
Nov 23 '18 at 23:39
|
show 7 more comments
A much simpler solution is to just decrease the length of the array by one. No need to create a second array.
function pop (array){
let last = array[array.length-1]; // Store last item in array
array.length = array.length > 0 ? array.length - 1 : 0; // Decrease length
return last; // Return last item
}
// Test function
function logger(ary){
console.log("Original array: " + ary.join(", "), "ntItem popped off: " + pop(ary), "ntArray contents now: " + ary.join(", "));
}
// Tests
var ary = [1,2,3,4]; logger(ary);
var ary = ["red", "white", "blue", "green"]; logger(ary);
var ary = ["onlyItem"]; logger(ary);
var ary = ; logger(ary);
var ary = [false]; logger(ary);answered Nov 23 '18 at 20:14
Scott MarcusScott Marcus
38.8k52036
1
@ScottMarcus justreturn last;
– Thomas
Nov 23 '18 at 20:34
@Thomas LOL, yeah. That works too!
– Scott Marcus
Nov 23 '18 at 20:35
add a comment |
It seems like simple is better in this case:
const example = [1,2,3,4];
function pop(arr) {
return arr && arr.splice(-1)[0]
}
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
// edge case: should it return undefined or should it throw?
console.log(pop())answered Nov 23 '18 at 20:31
Mark MeyerMark Meyer
38.4k33159
This is a really good take on the problem. Simple solution.
– Marius
Nov 24 '18 at 19:21
Thanks, i learnt something.
– Marius
Nov 24 '18 at 19:22
add a comment |
I think what you are looking for is Array.prototype.slice(). You can use the length property of the array to determine whether it is empty and then return the last entry using slice.
const example = [1,2,3,4];
const emptyExample = ;
const pop = group => group.length > 0
? group.slice(group.length - 1)[0]
: undefined;
const answers = [ pop(example), pop(emptyExample) ];
console.log(answers);Edit from comment
Example should remove from the array while returning last entry so Array.prototype.splice is probably the better function here.
const example = [1,2,3,4];
const emptyExample = ;
const pop = group => (Array.isArray(group) && group.length > 0)
? group.splice(group.length - 1, 1)[0]
: undefined;
const initialExample = [ ...example ];
const answers = [
pop(example),
pop(emptyExample),
{ initialExample, updatedExample: example, emptyExample }
];
console.log(answers);answered Nov 23 '18 at 20:19
D LowtherD Lowther
1,3181414
add a comment |
Array.prototype.splice(start[, deleteCount[, item1[, item2[, ...]]]])
The splice() method changes the contents of an array by removing existing elements and/or adding new elements.
...
Return value: An array containing the deleted elements. If only one element is removed, an array of one element is returned. If no elements are removed, an empty array is returned.
- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice
What this means is that so long as the input to the function is an instance of Array, we can call Array#splice(-1) to remove the last element. If there are no elements, this will return an empty array. Because we will always be getting either an array with one element or an empty array, we can access the first element using [0]. If the array is empty, this will be undefined.
So, check that that input is an array, then return Array#splice(-1)[0] if it is or undefined if it is not.
function pop(input) {
let output;
if(input instanceof Array) {
output = input.splice(-1)[0]
}
return output
}
function test(input) {
console.log({
before: input && Array.from(input),
popped: pop(input),
after: input
})
return test
}
test( [ 1, 2, 3, 4 ] )( [ 1 ] )( [ ] )( )( [ , , , ] )answered Nov 23 '18 at 20:46
Tiny GiantTiny Giant
13.4k64056
add a comment |
You could use Array.splice()
function pop(arr) {
return arr.splice(-1)[0];
}
This will delete the last item in the array and return it.
answered Nov 23 '18 at 20:19
oriontoriont
1239
This is pretty close, but has a couple of problems. The parameter name is not spelled consistently in the code, and if that is fixed, the return value is not correct. (It's almost correct, but read the problem description again.)
– Michael Geary
Nov 24 '18 at 4:24
add a comment |
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6 Answers
6
active
oldest
votes
6 Answers
6
active
oldest
votes
active
oldest
votes
active
oldest
votes
EDIT: This includes a null and empty check.
var array = [1, 2, 3, 4, 5];
function pop(array) {
return array && array.splice(-1)[0]
}
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(array);answered Nov 23 '18 at 20:15
MariusMarius
867
This doesn't meet the requirements
– Wayne Phipps
Nov 23 '18 at 20:23
2
Yep, now you're returning an array. :)
– Mark Meyer
Nov 23 '18 at 20:27
1
Haha @MarkMeyer , none of us are reading. Updated.
– Marius
Nov 23 '18 at 20:30
1
This worked, thanks so much!
– Marsden Mars
Nov 23 '18 at 20:32
1
@Marius Try repeating theconsole.log(pop(array))at the end of your snippet a few times, and then add aconsole.log(array)at the end, and see what it logs. Does the code do what the problem specification requires?
– Michael Geary
Nov 23 '18 at 23:39
|
show 7 more comments
EDIT: This includes a null and empty check.
var array = [1, 2, 3, 4, 5];
function pop(array) {
return array && array.splice(-1)[0]
}
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(array);answered Nov 23 '18 at 20:15
MariusMarius
867
This doesn't meet the requirements
– Wayne Phipps
Nov 23 '18 at 20:23
2
Yep, now you're returning an array. :)
– Mark Meyer
Nov 23 '18 at 20:27
1
Haha @MarkMeyer , none of us are reading. Updated.
– Marius
Nov 23 '18 at 20:30
1
This worked, thanks so much!
– Marsden Mars
Nov 23 '18 at 20:32
1
@Marius Try repeating theconsole.log(pop(array))at the end of your snippet a few times, and then add aconsole.log(array)at the end, and see what it logs. Does the code do what the problem specification requires?
– Michael Geary
Nov 23 '18 at 23:39
|
show 7 more comments
EDIT: This includes a null and empty check.
var array = [1, 2, 3, 4, 5];
function pop(array) {
return array && array.splice(-1)[0]
}
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(array);answered Nov 23 '18 at 20:15
MariusMarius
867
EDIT: This includes a null and empty check.
var array = [1, 2, 3, 4, 5];
function pop(array) {
return array && array.splice(-1)[0]
}
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(array);var array = [1, 2, 3, 4, 5];
function pop(array) {
return array && array.splice(-1)[0]
}
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(array);var array = [1, 2, 3, 4, 5];
function pop(array) {
return array && array.splice(-1)[0]
}
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(pop(array));
console.log(array);answered Nov 23 '18 at 20:15
MariusMarius
867
edited Nov 24 '18 at 19:33
answered Nov 23 '18 at 20:15
MariusMarius
867
answered Nov 23 '18 at 20:15
MariusMarius
867
answered Nov 23 '18 at 20:15
MariusMarius
867
867
This doesn't meet the requirements
– Wayne Phipps
Nov 23 '18 at 20:23
2
Yep, now you're returning an array. :)
– Mark Meyer
Nov 23 '18 at 20:27
1
Haha @MarkMeyer , none of us are reading. Updated.
– Marius
Nov 23 '18 at 20:30
1
This worked, thanks so much!
– Marsden Mars
Nov 23 '18 at 20:32
1
@Marius Try repeating theconsole.log(pop(array))at the end of your snippet a few times, and then add aconsole.log(array)at the end, and see what it logs. Does the code do what the problem specification requires?
– Michael Geary
Nov 23 '18 at 23:39
|
show 7 more comments
This doesn't meet the requirements
– Wayne Phipps
Nov 23 '18 at 20:23
2
Yep, now you're returning an array. :)
– Mark Meyer
Nov 23 '18 at 20:27
1
Haha @MarkMeyer , none of us are reading. Updated.
– Marius
Nov 23 '18 at 20:30
1
This worked, thanks so much!
– Marsden Mars
Nov 23 '18 at 20:32
1
@Marius Try repeating theconsole.log(pop(array))at the end of your snippet a few times, and then add aconsole.log(array)at the end, and see what it logs. Does the code do what the problem specification requires?
– Michael Geary
Nov 23 '18 at 23:39
This doesn't meet the requirements
– Wayne Phipps
Nov 23 '18 at 20:23
This doesn't meet the requirements
– Wayne Phipps
Nov 23 '18 at 20:23
2
2
Yep, now you're returning an array. :)
– Mark Meyer
Nov 23 '18 at 20:27
Yep, now you're returning an array. :)
– Mark Meyer
Nov 23 '18 at 20:27
1
1
Haha @MarkMeyer , none of us are reading. Updated.
– Marius
Nov 23 '18 at 20:30
Haha @MarkMeyer , none of us are reading. Updated.
– Marius
Nov 23 '18 at 20:30
1
1
This worked, thanks so much!
– Marsden Mars
Nov 23 '18 at 20:32
This worked, thanks so much!
– Marsden Mars
Nov 23 '18 at 20:32
1
1
@Marius Try repeating the
console.log(pop(array)) at the end of your snippet a few times, and then add a console.log(array) at the end, and see what it logs. Does the code do what the problem specification requires?– Michael Geary
Nov 23 '18 at 23:39
@Marius Try repeating the
console.log(pop(array)) at the end of your snippet a few times, and then add a console.log(array) at the end, and see what it logs. Does the code do what the problem specification requires?– Michael Geary
Nov 23 '18 at 23:39
|
show 7 more comments
A much simpler solution is to just decrease the length of the array by one. No need to create a second array.
function pop (array){
let last = array[array.length-1]; // Store last item in array
array.length = array.length > 0 ? array.length - 1 : 0; // Decrease length
return last; // Return last item
}
// Test function
function logger(ary){
console.log("Original array: " + ary.join(", "), "ntItem popped off: " + pop(ary), "ntArray contents now: " + ary.join(", "));
}
// Tests
var ary = [1,2,3,4]; logger(ary);
var ary = ["red", "white", "blue", "green"]; logger(ary);
var ary = ["onlyItem"]; logger(ary);
var ary = ; logger(ary);
var ary = [false]; logger(ary);answered Nov 23 '18 at 20:14
Scott MarcusScott Marcus
38.8k52036
1
@ScottMarcus justreturn last;
– Thomas
Nov 23 '18 at 20:34
@Thomas LOL, yeah. That works too!
– Scott Marcus
Nov 23 '18 at 20:35
add a comment |
A much simpler solution is to just decrease the length of the array by one. No need to create a second array.
function pop (array){
let last = array[array.length-1]; // Store last item in array
array.length = array.length > 0 ? array.length - 1 : 0; // Decrease length
return last; // Return last item
}
// Test function
function logger(ary){
console.log("Original array: " + ary.join(", "), "ntItem popped off: " + pop(ary), "ntArray contents now: " + ary.join(", "));
}
// Tests
var ary = [1,2,3,4]; logger(ary);
var ary = ["red", "white", "blue", "green"]; logger(ary);
var ary = ["onlyItem"]; logger(ary);
var ary = ; logger(ary);
var ary = [false]; logger(ary);answered Nov 23 '18 at 20:14
Scott MarcusScott Marcus
38.8k52036
1
@ScottMarcus justreturn last;
– Thomas
Nov 23 '18 at 20:34
@Thomas LOL, yeah. That works too!
– Scott Marcus
Nov 23 '18 at 20:35
add a comment |
A much simpler solution is to just decrease the length of the array by one. No need to create a second array.
function pop (array){
let last = array[array.length-1]; // Store last item in array
array.length = array.length > 0 ? array.length - 1 : 0; // Decrease length
return last; // Return last item
}
// Test function
function logger(ary){
console.log("Original array: " + ary.join(", "), "ntItem popped off: " + pop(ary), "ntArray contents now: " + ary.join(", "));
}
// Tests
var ary = [1,2,3,4]; logger(ary);
var ary = ["red", "white", "blue", "green"]; logger(ary);
var ary = ["onlyItem"]; logger(ary);
var ary = ; logger(ary);
var ary = [false]; logger(ary);answered Nov 23 '18 at 20:14
Scott MarcusScott Marcus
38.8k52036
A much simpler solution is to just decrease the length of the array by one. No need to create a second array.
function pop (array){
let last = array[array.length-1]; // Store last item in array
array.length = array.length > 0 ? array.length - 1 : 0; // Decrease length
return last; // Return last item
}
// Test function
function logger(ary){
console.log("Original array: " + ary.join(", "), "ntItem popped off: " + pop(ary), "ntArray contents now: " + ary.join(", "));
}
// Tests
var ary = [1,2,3,4]; logger(ary);
var ary = ["red", "white", "blue", "green"]; logger(ary);
var ary = ["onlyItem"]; logger(ary);
var ary = ; logger(ary);
var ary = [false]; logger(ary);function pop (array){
let last = array[array.length-1]; // Store last item in array
array.length = array.length > 0 ? array.length - 1 : 0; // Decrease length
return last; // Return last item
}
// Test function
function logger(ary){
console.log("Original array: " + ary.join(", "), "ntItem popped off: " + pop(ary), "ntArray contents now: " + ary.join(", "));
}
// Tests
var ary = [1,2,3,4]; logger(ary);
var ary = ["red", "white", "blue", "green"]; logger(ary);
var ary = ["onlyItem"]; logger(ary);
var ary = ; logger(ary);
var ary = [false]; logger(ary);function pop (array){
let last = array[array.length-1]; // Store last item in array
array.length = array.length > 0 ? array.length - 1 : 0; // Decrease length
return last; // Return last item
}
// Test function
function logger(ary){
console.log("Original array: " + ary.join(", "), "ntItem popped off: " + pop(ary), "ntArray contents now: " + ary.join(", "));
}
// Tests
var ary = [1,2,3,4]; logger(ary);
var ary = ["red", "white", "blue", "green"]; logger(ary);
var ary = ["onlyItem"]; logger(ary);
var ary = ; logger(ary);
var ary = [false]; logger(ary);answered Nov 23 '18 at 20:14
Scott MarcusScott Marcus
38.8k52036
edited Nov 23 '18 at 20:43
answered Nov 23 '18 at 20:14
Scott MarcusScott Marcus
38.8k52036
answered Nov 23 '18 at 20:14
Scott MarcusScott Marcus
38.8k52036
answered Nov 23 '18 at 20:14
Scott MarcusScott Marcus
38.8k52036
38.8k52036
1
@ScottMarcus justreturn last;
– Thomas
Nov 23 '18 at 20:34
@Thomas LOL, yeah. That works too!
– Scott Marcus
Nov 23 '18 at 20:35
add a comment |
1
@ScottMarcus justreturn last;
– Thomas
Nov 23 '18 at 20:34
@Thomas LOL, yeah. That works too!
– Scott Marcus
Nov 23 '18 at 20:35
1
1
@ScottMarcus just
return last;– Thomas
Nov 23 '18 at 20:34
@ScottMarcus just
return last;– Thomas
Nov 23 '18 at 20:34
@Thomas LOL, yeah. That works too!
– Scott Marcus
Nov 23 '18 at 20:35
@Thomas LOL, yeah. That works too!
– Scott Marcus
Nov 23 '18 at 20:35
add a comment |
It seems like simple is better in this case:
const example = [1,2,3,4];
function pop(arr) {
return arr && arr.splice(-1)[0]
}
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
// edge case: should it return undefined or should it throw?
console.log(pop())answered Nov 23 '18 at 20:31
Mark MeyerMark Meyer
38.4k33159
This is a really good take on the problem. Simple solution.
– Marius
Nov 24 '18 at 19:21
Thanks, i learnt something.
– Marius
Nov 24 '18 at 19:22
add a comment |
It seems like simple is better in this case:
const example = [1,2,3,4];
function pop(arr) {
return arr && arr.splice(-1)[0]
}
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
// edge case: should it return undefined or should it throw?
console.log(pop())answered Nov 23 '18 at 20:31
Mark MeyerMark Meyer
38.4k33159
This is a really good take on the problem. Simple solution.
– Marius
Nov 24 '18 at 19:21
Thanks, i learnt something.
– Marius
Nov 24 '18 at 19:22
add a comment |
It seems like simple is better in this case:
const example = [1,2,3,4];
function pop(arr) {
return arr && arr.splice(-1)[0]
}
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
// edge case: should it return undefined or should it throw?
console.log(pop())answered Nov 23 '18 at 20:31
Mark MeyerMark Meyer
38.4k33159
It seems like simple is better in this case:
const example = [1,2,3,4];
function pop(arr) {
return arr && arr.splice(-1)[0]
}
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
// edge case: should it return undefined or should it throw?
console.log(pop())const example = [1,2,3,4];
function pop(arr) {
return arr && arr.splice(-1)[0]
}
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
// edge case: should it return undefined or should it throw?
console.log(pop())const example = [1,2,3,4];
function pop(arr) {
return arr && arr.splice(-1)[0]
}
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
console.log(pop(example))
// edge case: should it return undefined or should it throw?
console.log(pop())answered Nov 23 '18 at 20:31
Mark MeyerMark Meyer
38.4k33159
edited Nov 23 '18 at 21:04
answered Nov 23 '18 at 20:31
Mark MeyerMark Meyer
38.4k33159
answered Nov 23 '18 at 20:31
Mark MeyerMark Meyer
38.4k33159
answered Nov 23 '18 at 20:31
Mark MeyerMark Meyer
38.4k33159
38.4k33159
This is a really good take on the problem. Simple solution.
– Marius
Nov 24 '18 at 19:21
Thanks, i learnt something.
– Marius
Nov 24 '18 at 19:22
add a comment |
This is a really good take on the problem. Simple solution.
– Marius
Nov 24 '18 at 19:21
Thanks, i learnt something.
– Marius
Nov 24 '18 at 19:22
This is a really good take on the problem. Simple solution.
– Marius
Nov 24 '18 at 19:21
This is a really good take on the problem. Simple solution.
– Marius
Nov 24 '18 at 19:21
Thanks, i learnt something.
– Marius
Nov 24 '18 at 19:22
Thanks, i learnt something.
– Marius
Nov 24 '18 at 19:22
add a comment |
I think what you are looking for is Array.prototype.slice(). You can use the length property of the array to determine whether it is empty and then return the last entry using slice.
const example = [1,2,3,4];
const emptyExample = ;
const pop = group => group.length > 0
? group.slice(group.length - 1)[0]
: undefined;
const answers = [ pop(example), pop(emptyExample) ];
console.log(answers);Edit from comment
Example should remove from the array while returning last entry so Array.prototype.splice is probably the better function here.
const example = [1,2,3,4];
const emptyExample = ;
const pop = group => (Array.isArray(group) && group.length > 0)
? group.splice(group.length - 1, 1)[0]
: undefined;
const initialExample = [ ...example ];
const answers = [
pop(example),
pop(emptyExample),
{ initialExample, updatedExample: example, emptyExample }
];
console.log(answers);answered Nov 23 '18 at 20:19
D LowtherD Lowther
1,3181414
add a comment |
I think what you are looking for is Array.prototype.slice(). You can use the length property of the array to determine whether it is empty and then return the last entry using slice.
const example = [1,2,3,4];
const emptyExample = ;
const pop = group => group.length > 0
? group.slice(group.length - 1)[0]
: undefined;
const answers = [ pop(example), pop(emptyExample) ];
console.log(answers);Edit from comment
Example should remove from the array while returning last entry so Array.prototype.splice is probably the better function here.
const example = [1,2,3,4];
const emptyExample = ;
const pop = group => (Array.isArray(group) && group.length > 0)
? group.splice(group.length - 1, 1)[0]
: undefined;
const initialExample = [ ...example ];
const answers = [
pop(example),
pop(emptyExample),
{ initialExample, updatedExample: example, emptyExample }
];
console.log(answers);answered Nov 23 '18 at 20:19
D LowtherD Lowther
1,3181414
add a comment |
I think what you are looking for is Array.prototype.slice(). You can use the length property of the array to determine whether it is empty and then return the last entry using slice.
const example = [1,2,3,4];
const emptyExample = ;
const pop = group => group.length > 0
? group.slice(group.length - 1)[0]
: undefined;
const answers = [ pop(example), pop(emptyExample) ];
console.log(answers);Edit from comment
Example should remove from the array while returning last entry so Array.prototype.splice is probably the better function here.
const example = [1,2,3,4];
const emptyExample = ;
const pop = group => (Array.isArray(group) && group.length > 0)
? group.splice(group.length - 1, 1)[0]
: undefined;
const initialExample = [ ...example ];
const answers = [
pop(example),
pop(emptyExample),
{ initialExample, updatedExample: example, emptyExample }
];
console.log(answers);answered Nov 23 '18 at 20:19
D LowtherD Lowther
1,3181414
I think what you are looking for is Array.prototype.slice(). You can use the length property of the array to determine whether it is empty and then return the last entry using slice.
const example = [1,2,3,4];
const emptyExample = ;
const pop = group => group.length > 0
? group.slice(group.length - 1)[0]
: undefined;
const answers = [ pop(example), pop(emptyExample) ];
console.log(answers);Edit from comment
Example should remove from the array while returning last entry so Array.prototype.splice is probably the better function here.
const example = [1,2,3,4];
const emptyExample = ;
const pop = group => (Array.isArray(group) && group.length > 0)
? group.splice(group.length - 1, 1)[0]
: undefined;
const initialExample = [ ...example ];
const answers = [
pop(example),
pop(emptyExample),
{ initialExample, updatedExample: example, emptyExample }
];
console.log(answers);const example = [1,2,3,4];
const emptyExample = ;
const pop = group => group.length > 0
? group.slice(group.length - 1)[0]
: undefined;
const answers = [ pop(example), pop(emptyExample) ];
console.log(answers);const example = [1,2,3,4];
const emptyExample = ;
const pop = group => group.length > 0
? group.slice(group.length - 1)[0]
: undefined;
const answers = [ pop(example), pop(emptyExample) ];
console.log(answers);const example = [1,2,3,4];
const emptyExample = ;
const pop = group => (Array.isArray(group) && group.length > 0)
? group.splice(group.length - 1, 1)[0]
: undefined;
const initialExample = [ ...example ];
const answers = [
pop(example),
pop(emptyExample),
{ initialExample, updatedExample: example, emptyExample }
];
console.log(answers);const example = [1,2,3,4];
const emptyExample = ;
const pop = group => (Array.isArray(group) && group.length > 0)
? group.splice(group.length - 1, 1)[0]
: undefined;
const initialExample = [ ...example ];
const answers = [
pop(example),
pop(emptyExample),
{ initialExample, updatedExample: example, emptyExample }
];
console.log(answers);answered Nov 23 '18 at 20:19
D LowtherD Lowther
1,3181414
edited Nov 23 '18 at 20:46
answered Nov 23 '18 at 20:19
D LowtherD Lowther
1,3181414
answered Nov 23 '18 at 20:19
D LowtherD Lowther
1,3181414
answered Nov 23 '18 at 20:19
D LowtherD Lowther
1,3181414
1,3181414
add a comment |
add a comment |
Array.prototype.splice(start[, deleteCount[, item1[, item2[, ...]]]])
The splice() method changes the contents of an array by removing existing elements and/or adding new elements.
...
Return value: An array containing the deleted elements. If only one element is removed, an array of one element is returned. If no elements are removed, an empty array is returned.
- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice
What this means is that so long as the input to the function is an instance of Array, we can call Array#splice(-1) to remove the last element. If there are no elements, this will return an empty array. Because we will always be getting either an array with one element or an empty array, we can access the first element using [0]. If the array is empty, this will be undefined.
So, check that that input is an array, then return Array#splice(-1)[0] if it is or undefined if it is not.
function pop(input) {
let output;
if(input instanceof Array) {
output = input.splice(-1)[0]
}
return output
}
function test(input) {
console.log({
before: input && Array.from(input),
popped: pop(input),
after: input
})
return test
}
test( [ 1, 2, 3, 4 ] )( [ 1 ] )( [ ] )( )( [ , , , ] )answered Nov 23 '18 at 20:46
Tiny GiantTiny Giant
13.4k64056
add a comment |
Array.prototype.splice(start[, deleteCount[, item1[, item2[, ...]]]])
The splice() method changes the contents of an array by removing existing elements and/or adding new elements.
...
Return value: An array containing the deleted elements. If only one element is removed, an array of one element is returned. If no elements are removed, an empty array is returned.
- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice
What this means is that so long as the input to the function is an instance of Array, we can call Array#splice(-1) to remove the last element. If there are no elements, this will return an empty array. Because we will always be getting either an array with one element or an empty array, we can access the first element using [0]. If the array is empty, this will be undefined.
So, check that that input is an array, then return Array#splice(-1)[0] if it is or undefined if it is not.
function pop(input) {
let output;
if(input instanceof Array) {
output = input.splice(-1)[0]
}
return output
}
function test(input) {
console.log({
before: input && Array.from(input),
popped: pop(input),
after: input
})
return test
}
test( [ 1, 2, 3, 4 ] )( [ 1 ] )( [ ] )( )( [ , , , ] )answered Nov 23 '18 at 20:46
Tiny GiantTiny Giant
13.4k64056
add a comment |
Array.prototype.splice(start[, deleteCount[, item1[, item2[, ...]]]])
The splice() method changes the contents of an array by removing existing elements and/or adding new elements.
...
Return value: An array containing the deleted elements. If only one element is removed, an array of one element is returned. If no elements are removed, an empty array is returned.
- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice
What this means is that so long as the input to the function is an instance of Array, we can call Array#splice(-1) to remove the last element. If there are no elements, this will return an empty array. Because we will always be getting either an array with one element or an empty array, we can access the first element using [0]. If the array is empty, this will be undefined.
So, check that that input is an array, then return Array#splice(-1)[0] if it is or undefined if it is not.
function pop(input) {
let output;
if(input instanceof Array) {
output = input.splice(-1)[0]
}
return output
}
function test(input) {
console.log({
before: input && Array.from(input),
popped: pop(input),
after: input
})
return test
}
test( [ 1, 2, 3, 4 ] )( [ 1 ] )( [ ] )( )( [ , , , ] )answered Nov 23 '18 at 20:46
Tiny GiantTiny Giant
13.4k64056
Array.prototype.splice(start[, deleteCount[, item1[, item2[, ...]]]])
The splice() method changes the contents of an array by removing existing elements and/or adding new elements.
...
Return value: An array containing the deleted elements. If only one element is removed, an array of one element is returned. If no elements are removed, an empty array is returned.
- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice
What this means is that so long as the input to the function is an instance of Array, we can call Array#splice(-1) to remove the last element. If there are no elements, this will return an empty array. Because we will always be getting either an array with one element or an empty array, we can access the first element using [0]. If the array is empty, this will be undefined.
So, check that that input is an array, then return Array#splice(-1)[0] if it is or undefined if it is not.
function pop(input) {
let output;
if(input instanceof Array) {
output = input.splice(-1)[0]
}
return output
}
function test(input) {
console.log({
before: input && Array.from(input),
popped: pop(input),
after: input
})
return test
}
test( [ 1, 2, 3, 4 ] )( [ 1 ] )( [ ] )( )( [ , , , ] )function pop(input) {
let output;
if(input instanceof Array) {
output = input.splice(-1)[0]
}
return output
}
function test(input) {
console.log({
before: input && Array.from(input),
popped: pop(input),
after: input
})
return test
}
test( [ 1, 2, 3, 4 ] )( [ 1 ] )( [ ] )( )( [ , , , ] )function pop(input) {
let output;
if(input instanceof Array) {
output = input.splice(-1)[0]
}
return output
}
function test(input) {
console.log({
before: input && Array.from(input),
popped: pop(input),
after: input
})
return test
}
test( [ 1, 2, 3, 4 ] )( [ 1 ] )( [ ] )( )( [ , , , ] )answered Nov 23 '18 at 20:46
Tiny GiantTiny Giant
13.4k64056
answered Nov 23 '18 at 20:46
Tiny GiantTiny Giant
13.4k64056
answered Nov 23 '18 at 20:46
Tiny GiantTiny Giant
13.4k64056
answered Nov 23 '18 at 20:46
Tiny GiantTiny Giant
13.4k64056
13.4k64056
add a comment |
add a comment |
You could use Array.splice()
function pop(arr) {
return arr.splice(-1)[0];
}
This will delete the last item in the array and return it.
answered Nov 23 '18 at 20:19
oriontoriont
1239
This is pretty close, but has a couple of problems. The parameter name is not spelled consistently in the code, and if that is fixed, the return value is not correct. (It's almost correct, but read the problem description again.)
– Michael Geary
Nov 24 '18 at 4:24
add a comment |
You could use Array.splice()
function pop(arr) {
return arr.splice(-1)[0];
}
This will delete the last item in the array and return it.
answered Nov 23 '18 at 20:19
oriontoriont
1239
This is pretty close, but has a couple of problems. The parameter name is not spelled consistently in the code, and if that is fixed, the return value is not correct. (It's almost correct, but read the problem description again.)
– Michael Geary
Nov 24 '18 at 4:24
add a comment |
You could use Array.splice()
function pop(arr) {
return arr.splice(-1)[0];
}
This will delete the last item in the array and return it.
answered Nov 23 '18 at 20:19
oriontoriont
1239
You could use Array.splice()
function pop(arr) {
return arr.splice(-1)[0];
}
This will delete the last item in the array and return it.
answered Nov 23 '18 at 20:19
oriontoriont
1239
edited Nov 25 '18 at 17:06
answered Nov 23 '18 at 20:19
oriontoriont
1239
answered Nov 23 '18 at 20:19
oriontoriont
1239
answered Nov 23 '18 at 20:19
oriontoriont
1239
1239
This is pretty close, but has a couple of problems. The parameter name is not spelled consistently in the code, and if that is fixed, the return value is not correct. (It's almost correct, but read the problem description again.)
– Michael Geary
Nov 24 '18 at 4:24
add a comment |
This is pretty close, but has a couple of problems. The parameter name is not spelled consistently in the code, and if that is fixed, the return value is not correct. (It's almost correct, but read the problem description again.)
– Michael Geary
Nov 24 '18 at 4:24
This is pretty close, but has a couple of problems. The parameter name is not spelled consistently in the code, and if that is fixed, the return value is not correct. (It's almost correct, but read the problem description again.)
– Michael Geary
Nov 24 '18 at 4:24
This is pretty close, but has a couple of problems. The parameter name is not spelled consistently in the code, and if that is fixed, the return value is not correct. (It's almost correct, but read the problem description again.)
– Michael Geary
Nov 24 '18 at 4:24
add a comment |
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1
Try with
slice()... developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…– LGSon
Nov 23 '18 at 20:12
simple,
array.reverse().shift()then reverse it again..– rlemon
Nov 23 '18 at 20:15
First check the array length. If it is zero, return undefined. Otherwise, save the last array element in a local variable (using length-1 to access it). Then decrement the length, and return that local variable.
– Michael Geary
Nov 23 '18 at 20:21