Does Javascript have something similar to python's dict comprehension? [duplicate]
0
This question already has an answer here:
How to group an array of objects by key
11 answers
I have a set of data I'm collecting that outputs something like this:
[
{
hostName: 'server1',
service: 'service1',
perfData: 'unique string5',
state: 1
},
{
hostName: 'server1',
service: 'service2',
perfData: 'unique string4',
state: 1
},
{
hostName: 'server1',
service: 'service3',
perfData: 'unique string3',
state: 1
},
{
hostName: 'server2',
service: 'service1',
perfData: 'unique string2',
state: 1
},
{
hostName: 'server2',
service: 'service2',
perfData: 'unique string1',
state: 1
}
]
I'm trying to loop through this array of objects with javascript to output the following:
let desiredOutput = [{'server1': [{
service: 'service1',
perfData: 'unique string1',
state: 1
},
{
service: 'service2',
perfData: 'unique string1',
state: 1
},
{
service: 'service3',
perfData: 'unique string1',
state: 1
}],
'server2': {
service: 'service1',
perfData: 'unique string1',
state: 1
}
}];
Does Javascript have something similar to dict comprehension? Not sure how to loop through an array of objects and merge them and make them an object with an array of objects. In python I could use something like this:
raw_data = [{'hostName': 'server1', 'serviceName': 'service1'}, {'hostName': 'server1', 'serviceName': 'service2'}, {'hostName': 'server1', 'serviceName': 'service3'}, {'hostName': 'server2', 'serviceName': 'service1'}, {'hostName': 'server2', 'serviceName': 'service2'}]
services = defaultdict(list)
for service in raw_data:
host_name = service.get('hostName')
service_name = service.get('service')
new_dict = {'hostName': host_name, 'serviceName': service_name}
services[new_dict['hostName']].append(new_dict)
print(services)
I found something close with this Merge javascript objects in array with same key but not quite what I'm looking for.
javascript arrays sorting object dictionary-comprehension
asked Nov 20 at 21:09
Ian Clark
32
marked as duplicate by trincot arrays
Users with the arrays badge can single-handedly close arrays questions as duplicates and reopen them as needed.
StackExchange.ready(function() {
if (StackExchange.options.isMobile) return;
$('.dupe-hammer-message-hover:not(.hover-bound)').each(function() {
var $hover = $(this).addClass('hover-bound'),
$msg = $hover.siblings('.dupe-hammer-message');
$hover.hover(
function() {
$hover.showInfoMessage('', {
messageElement: $msg.clone().show(),
transient: false,
position: { my: 'bottom left', at: 'top center', offsetTop: -7 },
dismissable: false,
relativeToBody: true
});
},
function() {
StackExchange.helpers.removeMessages();
}
);
});
});
Nov 20 at 21:25
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
add a comment |
0
This question already has an answer here:
How to group an array of objects by key
11 answers
I have a set of data I'm collecting that outputs something like this:
[
{
hostName: 'server1',
service: 'service1',
perfData: 'unique string5',
state: 1
},
{
hostName: 'server1',
service: 'service2',
perfData: 'unique string4',
state: 1
},
{
hostName: 'server1',
service: 'service3',
perfData: 'unique string3',
state: 1
},
{
hostName: 'server2',
service: 'service1',
perfData: 'unique string2',
state: 1
},
{
hostName: 'server2',
service: 'service2',
perfData: 'unique string1',
state: 1
}
]
I'm trying to loop through this array of objects with javascript to output the following:
let desiredOutput = [{'server1': [{
service: 'service1',
perfData: 'unique string1',
state: 1
},
{
service: 'service2',
perfData: 'unique string1',
state: 1
},
{
service: 'service3',
perfData: 'unique string1',
state: 1
}],
'server2': {
service: 'service1',
perfData: 'unique string1',
state: 1
}
}];
Does Javascript have something similar to dict comprehension? Not sure how to loop through an array of objects and merge them and make them an object with an array of objects. In python I could use something like this:
raw_data = [{'hostName': 'server1', 'serviceName': 'service1'}, {'hostName': 'server1', 'serviceName': 'service2'}, {'hostName': 'server1', 'serviceName': 'service3'}, {'hostName': 'server2', 'serviceName': 'service1'}, {'hostName': 'server2', 'serviceName': 'service2'}]
services = defaultdict(list)
for service in raw_data:
host_name = service.get('hostName')
service_name = service.get('service')
new_dict = {'hostName': host_name, 'serviceName': service_name}
services[new_dict['hostName']].append(new_dict)
print(services)
I found something close with this Merge javascript objects in array with same key but not quite what I'm looking for.
javascript arrays sorting object dictionary-comprehension
asked Nov 20 at 21:09
Ian Clark
32
marked as duplicate by trincot arrays
Users with the arrays badge can single-handedly close arrays questions as duplicates and reopen them as needed.
StackExchange.ready(function() {
if (StackExchange.options.isMobile) return;
$('.dupe-hammer-message-hover:not(.hover-bound)').each(function() {
var $hover = $(this).addClass('hover-bound'),
$msg = $hover.siblings('.dupe-hammer-message');
$hover.hover(
function() {
$hover.showInfoMessage('', {
messageElement: $msg.clone().show(),
transient: false,
position: { my: 'bottom left', at: 'top center', offsetTop: -7 },
dismissable: false,
relativeToBody: true
});
},
function() {
StackExchange.helpers.removeMessages();
}
);
});
});
Nov 20 at 21:25
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
JavaScript has several built inArray.prototypemethods for traverse and transforming arrays. More information can be found at the MDN for Arrays developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…
– Robert Mennell
Nov 20 at 21:16
Also in JavaScript we just access them using the bracket notation:object[key]orobject.keyif the key is known. As for making a new object, object literals are allowed to use computed values{ [key] : value }and more information can be found here: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…
– Robert Mennell
Nov 20 at 21:20
The Python code you posted does not have a "dict comprehension". You are iterating in a conventionalforloop and then building yourservicesdictionary. With Javascript, the most appropriate array method for this case seems likereduce.
– slider
Nov 20 at 21:22
I don't see how this relates to dict comprehension as your Python snippet does not use it. Python dict comprehension looks like{ key: value for key, value in iterable }
– trincot
Nov 20 at 21:23
Shouldn't your result include{"service": "service2", "perfData": "unique string1", "state": 1}in theserver2key?
– ggorlen
Nov 20 at 21:28
add a comment |
0
0
0
This question already has an answer here:
How to group an array of objects by key
11 answers
I have a set of data I'm collecting that outputs something like this:
[
{
hostName: 'server1',
service: 'service1',
perfData: 'unique string5',
state: 1
},
{
hostName: 'server1',
service: 'service2',
perfData: 'unique string4',
state: 1
},
{
hostName: 'server1',
service: 'service3',
perfData: 'unique string3',
state: 1
},
{
hostName: 'server2',
service: 'service1',
perfData: 'unique string2',
state: 1
},
{
hostName: 'server2',
service: 'service2',
perfData: 'unique string1',
state: 1
}
]
I'm trying to loop through this array of objects with javascript to output the following:
let desiredOutput = [{'server1': [{
service: 'service1',
perfData: 'unique string1',
state: 1
},
{
service: 'service2',
perfData: 'unique string1',
state: 1
},
{
service: 'service3',
perfData: 'unique string1',
state: 1
}],
'server2': {
service: 'service1',
perfData: 'unique string1',
state: 1
}
}];
Does Javascript have something similar to dict comprehension? Not sure how to loop through an array of objects and merge them and make them an object with an array of objects. In python I could use something like this:
raw_data = [{'hostName': 'server1', 'serviceName': 'service1'}, {'hostName': 'server1', 'serviceName': 'service2'}, {'hostName': 'server1', 'serviceName': 'service3'}, {'hostName': 'server2', 'serviceName': 'service1'}, {'hostName': 'server2', 'serviceName': 'service2'}]
services = defaultdict(list)
for service in raw_data:
host_name = service.get('hostName')
service_name = service.get('service')
new_dict = {'hostName': host_name, 'serviceName': service_name}
services[new_dict['hostName']].append(new_dict)
print(services)
I found something close with this Merge javascript objects in array with same key but not quite what I'm looking for.
javascript arrays sorting object dictionary-comprehension
asked Nov 20 at 21:09
Ian Clark
32
This question already has an answer here:
How to group an array of objects by key
11 answers
I have a set of data I'm collecting that outputs something like this:
[
{
hostName: 'server1',
service: 'service1',
perfData: 'unique string5',
state: 1
},
{
hostName: 'server1',
service: 'service2',
perfData: 'unique string4',
state: 1
},
{
hostName: 'server1',
service: 'service3',
perfData: 'unique string3',
state: 1
},
{
hostName: 'server2',
service: 'service1',
perfData: 'unique string2',
state: 1
},
{
hostName: 'server2',
service: 'service2',
perfData: 'unique string1',
state: 1
}
]
I'm trying to loop through this array of objects with javascript to output the following:
let desiredOutput = [{'server1': [{
service: 'service1',
perfData: 'unique string1',
state: 1
},
{
service: 'service2',
perfData: 'unique string1',
state: 1
},
{
service: 'service3',
perfData: 'unique string1',
state: 1
}],
'server2': {
service: 'service1',
perfData: 'unique string1',
state: 1
}
}];
Does Javascript have something similar to dict comprehension? Not sure how to loop through an array of objects and merge them and make them an object with an array of objects. In python I could use something like this:
raw_data = [{'hostName': 'server1', 'serviceName': 'service1'}, {'hostName': 'server1', 'serviceName': 'service2'}, {'hostName': 'server1', 'serviceName': 'service3'}, {'hostName': 'server2', 'serviceName': 'service1'}, {'hostName': 'server2', 'serviceName': 'service2'}]
services = defaultdict(list)
for service in raw_data:
host_name = service.get('hostName')
service_name = service.get('service')
new_dict = {'hostName': host_name, 'serviceName': service_name}
services[new_dict['hostName']].append(new_dict)
print(services)
I found something close with this Merge javascript objects in array with same key but not quite what I'm looking for.
This question already has an answer here:
How to group an array of objects by key
11 answers
javascript arrays sorting object dictionary-comprehension
javascript arrays sorting object dictionary-comprehension
asked Nov 20 at 21:09
Ian Clark
32
asked Nov 20 at 21:09
Ian Clark
32
asked Nov 20 at 21:09
Ian Clark
32
asked Nov 20 at 21:09
Ian Clark
32
asked Nov 20 at 21:09
Ian Clark
32
32
marked as duplicate by trincot arrays
Users with the arrays badge can single-handedly close arrays questions as duplicates and reopen them as needed.
StackExchange.ready(function() {
if (StackExchange.options.isMobile) return;
$('.dupe-hammer-message-hover:not(.hover-bound)').each(function() {
var $hover = $(this).addClass('hover-bound'),
$msg = $hover.siblings('.dupe-hammer-message');
$hover.hover(
function() {
$hover.showInfoMessage('', {
messageElement: $msg.clone().show(),
transient: false,
position: { my: 'bottom left', at: 'top center', offsetTop: -7 },
dismissable: false,
relativeToBody: true
});
},
function() {
StackExchange.helpers.removeMessages();
}
);
});
});
Nov 20 at 21:25
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
marked as duplicate by trincot arrays
Users with the arrays badge can single-handedly close arrays questions as duplicates and reopen them as needed.
StackExchange.ready(function() {
if (StackExchange.options.isMobile) return;
$('.dupe-hammer-message-hover:not(.hover-bound)').each(function() {
var $hover = $(this).addClass('hover-bound'),
$msg = $hover.siblings('.dupe-hammer-message');
$hover.hover(
function() {
$hover.showInfoMessage('', {
messageElement: $msg.clone().show(),
transient: false,
position: { my: 'bottom left', at: 'top center', offsetTop: -7 },
dismissable: false,
relativeToBody: true
});
},
function() {
StackExchange.helpers.removeMessages();
}
);
});
});
Nov 20 at 21:25
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
JavaScript has several built inArray.prototypemethods for traverse and transforming arrays. More information can be found at the MDN for Arrays developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…
– Robert Mennell
Nov 20 at 21:16
Also in JavaScript we just access them using the bracket notation:object[key]orobject.keyif the key is known. As for making a new object, object literals are allowed to use computed values{ [key] : value }and more information can be found here: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…
– Robert Mennell
Nov 20 at 21:20
The Python code you posted does not have a "dict comprehension". You are iterating in a conventionalforloop and then building yourservicesdictionary. With Javascript, the most appropriate array method for this case seems likereduce.
– slider
Nov 20 at 21:22
I don't see how this relates to dict comprehension as your Python snippet does not use it. Python dict comprehension looks like{ key: value for key, value in iterable }
– trincot
Nov 20 at 21:23
Shouldn't your result include{"service": "service2", "perfData": "unique string1", "state": 1}in theserver2key?
– ggorlen
Nov 20 at 21:28
add a comment |
JavaScript has several built inArray.prototypemethods for traverse and transforming arrays. More information can be found at the MDN for Arrays developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…
– Robert Mennell
Nov 20 at 21:16
Also in JavaScript we just access them using the bracket notation:object[key]orobject.keyif the key is known. As for making a new object, object literals are allowed to use computed values{ [key] : value }and more information can be found here: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…
– Robert Mennell
Nov 20 at 21:20
The Python code you posted does not have a "dict comprehension". You are iterating in a conventionalforloop and then building yourservicesdictionary. With Javascript, the most appropriate array method for this case seems likereduce.
– slider
Nov 20 at 21:22
I don't see how this relates to dict comprehension as your Python snippet does not use it. Python dict comprehension looks like{ key: value for key, value in iterable }
– trincot
Nov 20 at 21:23
Shouldn't your result include{"service": "service2", "perfData": "unique string1", "state": 1}in theserver2key?
– ggorlen
Nov 20 at 21:28
JavaScript has several built in
Array.prototype methods for traverse and transforming arrays. More information can be found at the MDN for Arrays developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…– Robert Mennell
Nov 20 at 21:16
JavaScript has several built in
Array.prototype methods for traverse and transforming arrays. More information can be found at the MDN for Arrays developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…– Robert Mennell
Nov 20 at 21:16
Also in JavaScript we just access them using the bracket notation:
object[key] or object.key if the key is known. As for making a new object, object literals are allowed to use computed values { [key] : value } and more information can be found here: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…– Robert Mennell
Nov 20 at 21:20
Also in JavaScript we just access them using the bracket notation:
object[key] or object.key if the key is known. As for making a new object, object literals are allowed to use computed values { [key] : value } and more information can be found here: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…– Robert Mennell
Nov 20 at 21:20
The Python code you posted does not have a "dict comprehension". You are iterating in a conventional
for loop and then building your services dictionary. With Javascript, the most appropriate array method for this case seems like reduce.– slider
Nov 20 at 21:22
The Python code you posted does not have a "dict comprehension". You are iterating in a conventional
for loop and then building your services dictionary. With Javascript, the most appropriate array method for this case seems like reduce.– slider
Nov 20 at 21:22
I don't see how this relates to dict comprehension as your Python snippet does not use it. Python dict comprehension looks like
{ key: value for key, value in iterable }– trincot
Nov 20 at 21:23
I don't see how this relates to dict comprehension as your Python snippet does not use it. Python dict comprehension looks like
{ key: value for key, value in iterable }– trincot
Nov 20 at 21:23
Shouldn't your result include
{"service": "service2", "perfData": "unique string1", "state": 1} in the server2 key?– ggorlen
Nov 20 at 21:28
Shouldn't your result include
{"service": "service2", "perfData": "unique string1", "state": 1} in the server2 key?– ggorlen
Nov 20 at 21:28
add a comment |
1 Answer
1
active
oldest
votes
0
Your output structure is a bit strange (an array of one element?). Using reduce is a reasonable approach, building arrays for each unique key:
const data = [ { hostName: 'server1', service: 'service1', perfData: 'unique string5', state: 1 }, { hostName: 'server1', service: 'service2', perfData: 'unique string4', state: 1 }, { hostName: 'server1', service: 'service3', perfData: 'unique string3', state: 1 }, { hostName: 'server2', service: 'service1', perfData: 'unique string2', state: 1 }, { hostName: 'server2', service: 'service2', perfData: 'unique string1', state: 1 } ];
console.log([data.reduce((a, e) => {
const name = e.hostName;
delete e.hostName;
a[name] = name in a ? a[name].push(e) && a[name] : [e];
return a;
}, {})]);answered Nov 20 at 21:20
ggorlen
6,3413825
why nota[name] = name in a ? [...a[name], e] : [e];if you want to make concatenation smaller, or usea[name] = name in a ? a[name].push(e) && a[name] : [e];so that you can avoid the complexity problem your example introduces?
– Robert Mennell
Nov 20 at 21:23
All three options seem more or less the same complexity level to my mind, but thanks for the alternatives.
– ggorlen
Nov 20 at 21:26
[...a[name], e]will create a new array, traverse the original, then push the new element.a[name].concat([e])will create a new array by traversing the first to copy it, and then traverse the second to push(most complex).a[name].push(e) && a[name]will push onto the array and then return it(least complex). All three have slightly different complexity
– Robert Mennell
Nov 20 at 21:46
1
Oh, you're talking about time complexity/efficiency--I thought you were talking readability. That's fair enough.
– ggorlen
Nov 20 at 21:52
add a comment |
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
0
Your output structure is a bit strange (an array of one element?). Using reduce is a reasonable approach, building arrays for each unique key:
const data = [ { hostName: 'server1', service: 'service1', perfData: 'unique string5', state: 1 }, { hostName: 'server1', service: 'service2', perfData: 'unique string4', state: 1 }, { hostName: 'server1', service: 'service3', perfData: 'unique string3', state: 1 }, { hostName: 'server2', service: 'service1', perfData: 'unique string2', state: 1 }, { hostName: 'server2', service: 'service2', perfData: 'unique string1', state: 1 } ];
console.log([data.reduce((a, e) => {
const name = e.hostName;
delete e.hostName;
a[name] = name in a ? a[name].push(e) && a[name] : [e];
return a;
}, {})]);answered Nov 20 at 21:20
ggorlen
6,3413825
why nota[name] = name in a ? [...a[name], e] : [e];if you want to make concatenation smaller, or usea[name] = name in a ? a[name].push(e) && a[name] : [e];so that you can avoid the complexity problem your example introduces?
– Robert Mennell
Nov 20 at 21:23
All three options seem more or less the same complexity level to my mind, but thanks for the alternatives.
– ggorlen
Nov 20 at 21:26
[...a[name], e]will create a new array, traverse the original, then push the new element.a[name].concat([e])will create a new array by traversing the first to copy it, and then traverse the second to push(most complex).a[name].push(e) && a[name]will push onto the array and then return it(least complex). All three have slightly different complexity
– Robert Mennell
Nov 20 at 21:46
1
Oh, you're talking about time complexity/efficiency--I thought you were talking readability. That's fair enough.
– ggorlen
Nov 20 at 21:52
add a comment |
0
Your output structure is a bit strange (an array of one element?). Using reduce is a reasonable approach, building arrays for each unique key:
const data = [ { hostName: 'server1', service: 'service1', perfData: 'unique string5', state: 1 }, { hostName: 'server1', service: 'service2', perfData: 'unique string4', state: 1 }, { hostName: 'server1', service: 'service3', perfData: 'unique string3', state: 1 }, { hostName: 'server2', service: 'service1', perfData: 'unique string2', state: 1 }, { hostName: 'server2', service: 'service2', perfData: 'unique string1', state: 1 } ];
console.log([data.reduce((a, e) => {
const name = e.hostName;
delete e.hostName;
a[name] = name in a ? a[name].push(e) && a[name] : [e];
return a;
}, {})]);answered Nov 20 at 21:20
ggorlen
6,3413825
why nota[name] = name in a ? [...a[name], e] : [e];if you want to make concatenation smaller, or usea[name] = name in a ? a[name].push(e) && a[name] : [e];so that you can avoid the complexity problem your example introduces?
– Robert Mennell
Nov 20 at 21:23
All three options seem more or less the same complexity level to my mind, but thanks for the alternatives.
– ggorlen
Nov 20 at 21:26
[...a[name], e]will create a new array, traverse the original, then push the new element.a[name].concat([e])will create a new array by traversing the first to copy it, and then traverse the second to push(most complex).a[name].push(e) && a[name]will push onto the array and then return it(least complex). All three have slightly different complexity
– Robert Mennell
Nov 20 at 21:46
1
Oh, you're talking about time complexity/efficiency--I thought you were talking readability. That's fair enough.
– ggorlen
Nov 20 at 21:52
add a comment |
0
0
0
Your output structure is a bit strange (an array of one element?). Using reduce is a reasonable approach, building arrays for each unique key:
const data = [ { hostName: 'server1', service: 'service1', perfData: 'unique string5', state: 1 }, { hostName: 'server1', service: 'service2', perfData: 'unique string4', state: 1 }, { hostName: 'server1', service: 'service3', perfData: 'unique string3', state: 1 }, { hostName: 'server2', service: 'service1', perfData: 'unique string2', state: 1 }, { hostName: 'server2', service: 'service2', perfData: 'unique string1', state: 1 } ];
console.log([data.reduce((a, e) => {
const name = e.hostName;
delete e.hostName;
a[name] = name in a ? a[name].push(e) && a[name] : [e];
return a;
}, {})]);answered Nov 20 at 21:20
ggorlen
6,3413825
Your output structure is a bit strange (an array of one element?). Using reduce is a reasonable approach, building arrays for each unique key:
const data = [ { hostName: 'server1', service: 'service1', perfData: 'unique string5', state: 1 }, { hostName: 'server1', service: 'service2', perfData: 'unique string4', state: 1 }, { hostName: 'server1', service: 'service3', perfData: 'unique string3', state: 1 }, { hostName: 'server2', service: 'service1', perfData: 'unique string2', state: 1 }, { hostName: 'server2', service: 'service2', perfData: 'unique string1', state: 1 } ];
console.log([data.reduce((a, e) => {
const name = e.hostName;
delete e.hostName;
a[name] = name in a ? a[name].push(e) && a[name] : [e];
return a;
}, {})]);const data = [ { hostName: 'server1', service: 'service1', perfData: 'unique string5', state: 1 }, { hostName: 'server1', service: 'service2', perfData: 'unique string4', state: 1 }, { hostName: 'server1', service: 'service3', perfData: 'unique string3', state: 1 }, { hostName: 'server2', service: 'service1', perfData: 'unique string2', state: 1 }, { hostName: 'server2', service: 'service2', perfData: 'unique string1', state: 1 } ];
console.log([data.reduce((a, e) => {
const name = e.hostName;
delete e.hostName;
a[name] = name in a ? a[name].push(e) && a[name] : [e];
return a;
}, {})]);const data = [ { hostName: 'server1', service: 'service1', perfData: 'unique string5', state: 1 }, { hostName: 'server1', service: 'service2', perfData: 'unique string4', state: 1 }, { hostName: 'server1', service: 'service3', perfData: 'unique string3', state: 1 }, { hostName: 'server2', service: 'service1', perfData: 'unique string2', state: 1 }, { hostName: 'server2', service: 'service2', perfData: 'unique string1', state: 1 } ];
console.log([data.reduce((a, e) => {
const name = e.hostName;
delete e.hostName;
a[name] = name in a ? a[name].push(e) && a[name] : [e];
return a;
}, {})]);answered Nov 20 at 21:20
ggorlen
6,3413825
edited Nov 20 at 21:55
answered Nov 20 at 21:20
ggorlen
6,3413825
answered Nov 20 at 21:20
ggorlen
6,3413825
answered Nov 20 at 21:20
ggorlen
6,3413825
6,3413825
why nota[name] = name in a ? [...a[name], e] : [e];if you want to make concatenation smaller, or usea[name] = name in a ? a[name].push(e) && a[name] : [e];so that you can avoid the complexity problem your example introduces?
– Robert Mennell
Nov 20 at 21:23
All three options seem more or less the same complexity level to my mind, but thanks for the alternatives.
– ggorlen
Nov 20 at 21:26
[...a[name], e]will create a new array, traverse the original, then push the new element.a[name].concat([e])will create a new array by traversing the first to copy it, and then traverse the second to push(most complex).a[name].push(e) && a[name]will push onto the array and then return it(least complex). All three have slightly different complexity
– Robert Mennell
Nov 20 at 21:46
1
Oh, you're talking about time complexity/efficiency--I thought you were talking readability. That's fair enough.
– ggorlen
Nov 20 at 21:52
add a comment |
why nota[name] = name in a ? [...a[name], e] : [e];if you want to make concatenation smaller, or usea[name] = name in a ? a[name].push(e) && a[name] : [e];so that you can avoid the complexity problem your example introduces?
– Robert Mennell
Nov 20 at 21:23
All three options seem more or less the same complexity level to my mind, but thanks for the alternatives.
– ggorlen
Nov 20 at 21:26
[...a[name], e]will create a new array, traverse the original, then push the new element.a[name].concat([e])will create a new array by traversing the first to copy it, and then traverse the second to push(most complex).a[name].push(e) && a[name]will push onto the array and then return it(least complex). All three have slightly different complexity
– Robert Mennell
Nov 20 at 21:46
1
Oh, you're talking about time complexity/efficiency--I thought you were talking readability. That's fair enough.
– ggorlen
Nov 20 at 21:52
why not
a[name] = name in a ? [...a[name], e] : [e]; if you want to make concatenation smaller, or use a[name] = name in a ? a[name].push(e) && a[name] : [e]; so that you can avoid the complexity problem your example introduces?– Robert Mennell
Nov 20 at 21:23
why not
a[name] = name in a ? [...a[name], e] : [e]; if you want to make concatenation smaller, or use a[name] = name in a ? a[name].push(e) && a[name] : [e]; so that you can avoid the complexity problem your example introduces?– Robert Mennell
Nov 20 at 21:23
All three options seem more or less the same complexity level to my mind, but thanks for the alternatives.
– ggorlen
Nov 20 at 21:26
All three options seem more or less the same complexity level to my mind, but thanks for the alternatives.
– ggorlen
Nov 20 at 21:26
[...a[name], e] will create a new array, traverse the original, then push the new element. a[name].concat([e]) will create a new array by traversing the first to copy it, and then traverse the second to push(most complex). a[name].push(e) && a[name] will push onto the array and then return it(least complex). All three have slightly different complexity– Robert Mennell
Nov 20 at 21:46
[...a[name], e] will create a new array, traverse the original, then push the new element. a[name].concat([e]) will create a new array by traversing the first to copy it, and then traverse the second to push(most complex). a[name].push(e) && a[name] will push onto the array and then return it(least complex). All three have slightly different complexity– Robert Mennell
Nov 20 at 21:46
1
1
Oh, you're talking about time complexity/efficiency--I thought you were talking readability. That's fair enough.
– ggorlen
Nov 20 at 21:52
Oh, you're talking about time complexity/efficiency--I thought you were talking readability. That's fair enough.
– ggorlen
Nov 20 at 21:52
add a comment |
JavaScript has several built in
Array.prototypemethods for traverse and transforming arrays. More information can be found at the MDN for Arrays developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…– Robert Mennell
Nov 20 at 21:16
Also in JavaScript we just access them using the bracket notation:
object[key]orobject.keyif the key is known. As for making a new object, object literals are allowed to use computed values{ [key] : value }and more information can be found here: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…– Robert Mennell
Nov 20 at 21:20
The Python code you posted does not have a "dict comprehension". You are iterating in a conventional
forloop and then building yourservicesdictionary. With Javascript, the most appropriate array method for this case seems likereduce.– slider
Nov 20 at 21:22
I don't see how this relates to dict comprehension as your Python snippet does not use it. Python dict comprehension looks like
{ key: value for key, value in iterable }– trincot
Nov 20 at 21:23
Shouldn't your result include
{"service": "service2", "perfData": "unique string1", "state": 1}in theserver2key?– ggorlen
Nov 20 at 21:28