Prevent value of 0 evaluating to false when using logical OR

I am wondering if there was a way around this issue. I am currently storing a value in a variable like so:

Session['Score'] = 0;

Later I have an assignment like so:

Score = Session['Score'] || 'not set';

The problem is, when Session['Score'] is set to 0 as above, JavaScript will interpret it as:

Score = false || 'not set';

which means Score will evaluate to 'not set' instead of 0!

How can I get around this issue?

edited Nov 25 '18 at 0:26

Ivar

2,851113140

asked Nov 24 '18 at 21:56

James

315113

why not use a ternary ? you could use a negative value instead btw.

– Zohir Salak
Nov 24 '18 at 22:15

add a comment |

I am wondering if there was a way around this issue. I am currently storing a value in a variable like so:

Session['Score'] = 0;

Later I have an assignment like so:

Score = Session['Score'] || 'not set';

The problem is, when Session['Score'] is set to 0 as above, JavaScript will interpret it as:

Score = false || 'not set';

which means Score will evaluate to 'not set' instead of 0!

How can I get around this issue?

edited Nov 25 '18 at 0:26

Ivar

2,851113140

asked Nov 24 '18 at 21:56

James

315113

why not use a ternary ? you could use a negative value instead btw.

– Zohir Salak
Nov 24 '18 at 22:15

add a comment |

I am wondering if there was a way around this issue. I am currently storing a value in a variable like so:

Session['Score'] = 0;

Later I have an assignment like so:

Score = Session['Score'] || 'not set';

The problem is, when Session['Score'] is set to 0 as above, JavaScript will interpret it as:

Score = false || 'not set';

which means Score will evaluate to 'not set' instead of 0!

How can I get around this issue?

edited Nov 25 '18 at 0:26

Ivar

2,851113140

asked Nov 24 '18 at 21:56

James

315113

I am wondering if there was a way around this issue. I am currently storing a value in a variable like so:

Session['Score'] = 0;

Later I have an assignment like so:

Score = Session['Score'] || 'not set';

The problem is, when Session['Score'] is set to 0 as above, JavaScript will interpret it as:

Score = false || 'not set';

which means Score will evaluate to 'not set' instead of 0!

How can I get around this issue?

javascript boolean logical-operators short-circuiting

edited Nov 25 '18 at 0:26

Ivar

2,851113140

asked Nov 24 '18 at 21:56

James

315113

edited Nov 25 '18 at 0:26

Ivar

2,851113140

asked Nov 24 '18 at 21:56

James

315113

edited Nov 25 '18 at 0:26

Ivar

2,851113140

edited Nov 25 '18 at 0:26

Ivar

2,851113140

edited Nov 25 '18 at 0:26

Ivar

2,851113140

asked Nov 24 '18 at 21:56

James

315113

asked Nov 24 '18 at 21:56

James

315113

asked Nov 24 '18 at 21:56

James

315113

why not use a ternary ? you could use a negative value instead btw.

– Zohir Salak
Nov 24 '18 at 22:15

add a comment |

why not use a ternary ? you could use a negative value instead btw.

– Zohir Salak
Nov 24 '18 at 22:15

why not use a ternary ? you could use a negative value instead btw.

– Zohir Salak
Nov 24 '18 at 22:15

add a comment |

4 Answers
4

active

oldest

votes

You can do this with destructuring assignment:

let { Score = 'not set' } = Session;

If it's not set:

const Session = { };

let { Score = 'not set' } = Session;

console.log( Score );

If it is set to any value other than undefined, including falsy ones:

const Session = { Score: 0 };

let { Score = 'not set' } = Session;

console.log( Score );

edited Nov 24 '18 at 22:34

answered Nov 24 '18 at 22:28

Paulpro

114k15225230

add a comment |

The cleanest way is probably to set the value and then check if it is falsy but not equal to 0

let score = Session['Score'];



if (!score && score !== 0) {

  score = 'not set';

}

As mentioned by Patrick Roberts, you could also choose to use the ternary operator in combination with the in operator:

Score = 'Score' in Session ? Session.Score : 'not set'

edited Nov 24 '18 at 22:18

answered Nov 24 '18 at 22:12

Ivar

2,851113140

1

'Score' in Session ? Session.Score : 'not set'?

– Patrick Roberts
Nov 24 '18 at 22:13

add a comment |

You could be more explicit about your intent by creating a few functions:

function getScore(s)

{

    var result = s["Score"];

    if (result == null) {

        result = 0;

    }

    return result;

}



function addScore(s, v)

{

    var result = s["Score"];

    if (result == null) {

        result = 0;

    }

    result += v;

    s["Score"] = result;

    return result;

}



var Session = {};

document.write("Score ");

document.write(getScore(Session));

document.write("<p/>");

addScore(Session, 10);

document.write("Score ");

document.write(getScore(Session));

Expected output:

Score 0



Score 10

answered Nov 24 '18 at 22:11

Richard Hodges

56.2k658102

add a comment |

Use a string instead:

Session['Score'] = "0";



Score = Session['Score'] || 'not set';

edited Nov 24 '18 at 22:14

answered Nov 24 '18 at 21:57

Jack Bashford

9,40431540

1

@PatrickRoberts Really? Why? I thought that a string would fix it.

– Jack Bashford
Nov 24 '18 at 22:07

Really? You posted this as an answer without trying it first to see that it works?

– Patrick Roberts
Nov 24 '18 at 22:08

I don't have the code, and I don't know the OP's context, so I can't test it.

– Jack Bashford
Nov 24 '18 at 22:08

var Session = {}; Session['Score'] = "0"; var Score = parseInt(Session['Score']) || 'not set'; console.log(Score); Seems simple enough to create some context there.

– Patrick Roberts
Nov 24 '18 at 22:10

Wait a second. Look at my test web.edusercontent.com/d73ter2hovoc1fki8rqcb6m8dk/index.html

– Jack Bashford
Nov 24 '18 at 22:10

|
show 3 more comments

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4 Answers
4

active

oldest

votes

4 Answers
4

active

oldest

votes

You can do this with destructuring assignment:

let { Score = 'not set' } = Session;

If it's not set:

const Session = { };

let { Score = 'not set' } = Session;

console.log( Score );

If it is set to any value other than undefined, including falsy ones:

const Session = { Score: 0 };

let { Score = 'not set' } = Session;

console.log( Score );

edited Nov 24 '18 at 22:34

answered Nov 24 '18 at 22:28

Paulpro

114k15225230

add a comment |

You can do this with destructuring assignment:

let { Score = 'not set' } = Session;

If it's not set:

const Session = { };

let { Score = 'not set' } = Session;

console.log( Score );

If it is set to any value other than undefined, including falsy ones:

const Session = { Score: 0 };

let { Score = 'not set' } = Session;

console.log( Score );

edited Nov 24 '18 at 22:34

answered Nov 24 '18 at 22:28

Paulpro

114k15225230

add a comment |

You can do this with destructuring assignment:

let { Score = 'not set' } = Session;

If it's not set:

const Session = { };

let { Score = 'not set' } = Session;

console.log( Score );

If it is set to any value other than undefined, including falsy ones:

const Session = { Score: 0 };

let { Score = 'not set' } = Session;

console.log( Score );

edited Nov 24 '18 at 22:34

answered Nov 24 '18 at 22:28

Paulpro

114k15225230

You can do this with destructuring assignment:

let { Score = 'not set' } = Session;

If it's not set:

const Session = { };

let { Score = 'not set' } = Session;

console.log( Score );

If it is set to any value other than undefined, including falsy ones:

const Session = { Score: 0 };

let { Score = 'not set' } = Session;

console.log( Score );

const Session = { };

let { Score = 'not set' } = Session;

console.log( Score );

const Session = { };

let { Score = 'not set' } = Session;

console.log( Score );

const Session = { Score: 0 };

let { Score = 'not set' } = Session;

console.log( Score );

const Session = { Score: 0 };

let { Score = 'not set' } = Session;

console.log( Score );

edited Nov 24 '18 at 22:34

answered Nov 24 '18 at 22:28

Paulpro

114k15225230

edited Nov 24 '18 at 22:34

answered Nov 24 '18 at 22:28

Paulpro

114k15225230

answered Nov 24 '18 at 22:28

Paulpro

114k15225230

answered Nov 24 '18 at 22:28

Paulpro

114k15225230

add a comment |

The cleanest way is probably to set the value and then check if it is falsy but not equal to 0

let score = Session['Score'];



if (!score && score !== 0) {

  score = 'not set';

}

As mentioned by Patrick Roberts, you could also choose to use the ternary operator in combination with the in operator:

Score = 'Score' in Session ? Session.Score : 'not set'

edited Nov 24 '18 at 22:18

answered Nov 24 '18 at 22:12

Ivar

2,851113140

1

'Score' in Session ? Session.Score : 'not set'?

– Patrick Roberts
Nov 24 '18 at 22:13

add a comment |

The cleanest way is probably to set the value and then check if it is falsy but not equal to 0

let score = Session['Score'];



if (!score && score !== 0) {

  score = 'not set';

}

As mentioned by Patrick Roberts, you could also choose to use the ternary operator in combination with the in operator:

Score = 'Score' in Session ? Session.Score : 'not set'

edited Nov 24 '18 at 22:18

answered Nov 24 '18 at 22:12

Ivar

2,851113140

1

'Score' in Session ? Session.Score : 'not set'?

– Patrick Roberts
Nov 24 '18 at 22:13

add a comment |

The cleanest way is probably to set the value and then check if it is falsy but not equal to 0

let score = Session['Score'];



if (!score && score !== 0) {

  score = 'not set';

}

As mentioned by Patrick Roberts, you could also choose to use the ternary operator in combination with the in operator:

Score = 'Score' in Session ? Session.Score : 'not set'

edited Nov 24 '18 at 22:18

answered Nov 24 '18 at 22:12

Ivar

2,851113140

The cleanest way is probably to set the value and then check if it is falsy but not equal to 0

let score = Session['Score'];



if (!score && score !== 0) {

  score = 'not set';

}

As mentioned by Patrick Roberts, you could also choose to use the ternary operator in combination with the in operator:

Score = 'Score' in Session ? Session.Score : 'not set'

edited Nov 24 '18 at 22:18

answered Nov 24 '18 at 22:12

Ivar

2,851113140

edited Nov 24 '18 at 22:18

answered Nov 24 '18 at 22:12

Ivar

2,851113140

answered Nov 24 '18 at 22:12

Ivar

2,851113140

answered Nov 24 '18 at 22:12

Ivar

2,851113140

1

'Score' in Session ? Session.Score : 'not set'?

– Patrick Roberts
Nov 24 '18 at 22:13

add a comment |

1

'Score' in Session ? Session.Score : 'not set'?

– Patrick Roberts
Nov 24 '18 at 22:13

'Score' in Session ? Session.Score : 'not set'?

– Patrick Roberts
Nov 24 '18 at 22:13

add a comment |

You could be more explicit about your intent by creating a few functions:

function getScore(s)

{

    var result = s["Score"];

    if (result == null) {

        result = 0;

    }

    return result;

}



function addScore(s, v)

{

    var result = s["Score"];

    if (result == null) {

        result = 0;

    }

    result += v;

    s["Score"] = result;

    return result;

}



var Session = {};

document.write("Score ");

document.write(getScore(Session));

document.write("<p/>");

addScore(Session, 10);

document.write("Score ");

document.write(getScore(Session));

Expected output:

Score 0



Score 10

answered Nov 24 '18 at 22:11

Richard Hodges

56.2k658102

add a comment |

You could be more explicit about your intent by creating a few functions:

function getScore(s)

{

    var result = s["Score"];

    if (result == null) {

        result = 0;

    }

    return result;

}



function addScore(s, v)

{

    var result = s["Score"];

    if (result == null) {

        result = 0;

    }

    result += v;

    s["Score"] = result;

    return result;

}



var Session = {};

document.write("Score ");

document.write(getScore(Session));

document.write("<p/>");

addScore(Session, 10);

document.write("Score ");

document.write(getScore(Session));

Expected output:

Score 0



Score 10

answered Nov 24 '18 at 22:11

Richard Hodges

56.2k658102

add a comment |

You could be more explicit about your intent by creating a few functions:

function getScore(s)

{

    var result = s["Score"];

    if (result == null) {

        result = 0;

    }

    return result;

}



function addScore(s, v)

{

    var result = s["Score"];

    if (result == null) {

        result = 0;

    }

    result += v;

    s["Score"] = result;

    return result;

}



var Session = {};

document.write("Score ");

document.write(getScore(Session));

document.write("<p/>");

addScore(Session, 10);

document.write("Score ");

document.write(getScore(Session));

Expected output:

Score 0



Score 10

answered Nov 24 '18 at 22:11

Richard Hodges

56.2k658102

You could be more explicit about your intent by creating a few functions:

function getScore(s)

{

    var result = s["Score"];

    if (result == null) {

        result = 0;

    }

    return result;

}



function addScore(s, v)

{

    var result = s["Score"];

    if (result == null) {

        result = 0;

    }

    result += v;

    s["Score"] = result;

    return result;

}



var Session = {};

document.write("Score ");

document.write(getScore(Session));

document.write("<p/>");

addScore(Session, 10);

document.write("Score ");

document.write(getScore(Session));

Expected output:

Score 0



Score 10

answered Nov 24 '18 at 22:11

Richard Hodges

56.2k658102

answered Nov 24 '18 at 22:11

Richard Hodges

56.2k658102

answered Nov 24 '18 at 22:11

Richard Hodges

56.2k658102

answered Nov 24 '18 at 22:11

Richard Hodges

56.2k658102

add a comment |

Use a string instead:

Session['Score'] = "0";



Score = Session['Score'] || 'not set';

edited Nov 24 '18 at 22:14

answered Nov 24 '18 at 21:57

Jack Bashford

9,40431540

1

@PatrickRoberts Really? Why? I thought that a string would fix it.

– Jack Bashford
Nov 24 '18 at 22:07

Really? You posted this as an answer without trying it first to see that it works?

– Patrick Roberts
Nov 24 '18 at 22:08

I don't have the code, and I don't know the OP's context, so I can't test it.

– Jack Bashford
Nov 24 '18 at 22:08

var Session = {}; Session['Score'] = "0"; var Score = parseInt(Session['Score']) || 'not set'; console.log(Score); Seems simple enough to create some context there.

– Patrick Roberts
Nov 24 '18 at 22:10

Wait a second. Look at my test web.edusercontent.com/d73ter2hovoc1fki8rqcb6m8dk/index.html

– Jack Bashford
Nov 24 '18 at 22:10

|
show 3 more comments

Use a string instead:

Session['Score'] = "0";



Score = Session['Score'] || 'not set';

edited Nov 24 '18 at 22:14

answered Nov 24 '18 at 21:57

Jack Bashford

9,40431540

1

@PatrickRoberts Really? Why? I thought that a string would fix it.

– Jack Bashford
Nov 24 '18 at 22:07

Really? You posted this as an answer without trying it first to see that it works?

– Patrick Roberts
Nov 24 '18 at 22:08

I don't have the code, and I don't know the OP's context, so I can't test it.

– Jack Bashford
Nov 24 '18 at 22:08

var Session = {}; Session['Score'] = "0"; var Score = parseInt(Session['Score']) || 'not set'; console.log(Score); Seems simple enough to create some context there.

– Patrick Roberts
Nov 24 '18 at 22:10

Wait a second. Look at my test web.edusercontent.com/d73ter2hovoc1fki8rqcb6m8dk/index.html

– Jack Bashford
Nov 24 '18 at 22:10

|
show 3 more comments

Use a string instead:

Session['Score'] = "0";



Score = Session['Score'] || 'not set';

edited Nov 24 '18 at 22:14

answered Nov 24 '18 at 21:57

Jack Bashford

9,40431540

Use a string instead:

Session['Score'] = "0";



Score = Session['Score'] || 'not set';

edited Nov 24 '18 at 22:14

answered Nov 24 '18 at 21:57

Jack Bashford

9,40431540

edited Nov 24 '18 at 22:14

answered Nov 24 '18 at 21:57

Jack Bashford

9,40431540

answered Nov 24 '18 at 21:57

Jack Bashford

9,40431540

answered Nov 24 '18 at 21:57

Jack Bashford

9,40431540

1

@PatrickRoberts Really? Why? I thought that a string would fix it.

– Jack Bashford
Nov 24 '18 at 22:07

Really? You posted this as an answer without trying it first to see that it works?

– Patrick Roberts
Nov 24 '18 at 22:08

I don't have the code, and I don't know the OP's context, so I can't test it.

– Jack Bashford
Nov 24 '18 at 22:08

var Session = {}; Session['Score'] = "0"; var Score = parseInt(Session['Score']) || 'not set'; console.log(Score); Seems simple enough to create some context there.

– Patrick Roberts
Nov 24 '18 at 22:10

Wait a second. Look at my test web.edusercontent.com/d73ter2hovoc1fki8rqcb6m8dk/index.html

– Jack Bashford
Nov 24 '18 at 22:10

|
show 3 more comments

1

@PatrickRoberts Really? Why? I thought that a string would fix it.

– Jack Bashford
Nov 24 '18 at 22:07

Really? You posted this as an answer without trying it first to see that it works?

– Patrick Roberts
Nov 24 '18 at 22:08

I don't have the code, and I don't know the OP's context, so I can't test it.

– Jack Bashford
Nov 24 '18 at 22:08

var Session = {}; Session['Score'] = "0"; var Score = parseInt(Session['Score']) || 'not set'; console.log(Score); Seems simple enough to create some context there.

– Patrick Roberts
Nov 24 '18 at 22:10

Wait a second. Look at my test web.edusercontent.com/d73ter2hovoc1fki8rqcb6m8dk/index.html

– Jack Bashford
Nov 24 '18 at 22:10

@PatrickRoberts Really? Why? I thought that a string would fix it.

– Jack Bashford
Nov 24 '18 at 22:07

Really? You posted this as an answer without trying it first to see that it works?

– Patrick Roberts
Nov 24 '18 at 22:08

I don't have the code, and I don't know the OP's context, so I can't test it.

– Jack Bashford
Nov 24 '18 at 22:08

var Session = {}; Session['Score'] = "0"; var Score = parseInt(Session['Score']) || 'not set'; console.log(Score); Seems simple enough to create some context there.

– Patrick Roberts
Nov 24 '18 at 22:10

Wait a second. Look at my test web.edusercontent.com/d73ter2hovoc1fki8rqcb6m8dk/index.html

– Jack Bashford
Nov 24 '18 at 22:10

|
show 3 more comments

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