javascript null value in string

Question

In javascript I have the following:

var inf = id + '|' + city ;

if id or city are null then inf will be null.

Is there any slick way of saying if id or city are null make then blank.

I know in c# you can do the following:

var inf = (id ?? "") + (city ?? "");

Any similar method in javascript?

Your question is a bit confusing. Please provide one ore more example values for `inf`. — Felix Kling, Apr 06 '12 at 15:52
possible duplicate of [null coalescing operator for javascript?](http://stackoverflow.com/questions/476436/null-coalescing-operator-for-javascript) — , Apr 06 '12 at 16:26

psyho · Answer 1 · 2012-04-06T16:08:19.227

22

How about:

var inf = [id, city].join('|');

EDIT: You can remove the "blank" parts before joining, so that if only one of id and city is null, inf will just contain that part and if both are null inf will be empty.

var inf = _([id, city]).compact().join('|'); // underscore.js
var inf = [id, city].compact().join('|'); // sugar.js
var inf = [id, city].filter(function(str) { return str; }).join('|'); // without helpers

edited Apr 06 '12 at 16:08

answered Apr 06 '12 at 15:48

psyho

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`inf` will not be blank , if `id` and `city` are `null`s. – Engineer Apr 06 '12 at 15:54
@Engineer: Yes, it'll be `"|"`, the desired result. – gen_Eric Apr 06 '12 at 15:55
@Rocket I know about "|", just read `if id or city are null then inf will be null.` of @Nate. – Engineer Apr 06 '12 at 15:56

score 16 · Answer 2 · answered Apr 06 '12 at 15:47

16

Total long shot, but try this:

var inf = (id || "") + "|" + (city || "");

answered Apr 06 '12 at 15:47

Elliot Bonneville

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this will work for undefined vars, not so sure about null values. – Eliran Malka Apr 06 '12 at 15:48
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I'd suggest adding parenthesis: `var inf = (id || "") + "|" + (city || "");` – gen_Eric Apr 06 '12 at 15:48
@Rocket: Alright, thanks, although I don't think it would matter. – Elliot Bonneville Apr 06 '12 at 15:49
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@ElliotBonneville it doesn't actually matter to the interpreter (since it's equivalent), but it will matter to your co-workers. – nickf Apr 06 '12 at 15:50
@Rocket: Oh, okay. Thanks. **nickf**: That's true, that's true. :) – Elliot Bonneville Apr 06 '12 at 15:51
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@nickf It *does* make a difference. Try it. – NullUserException Apr 06 '12 at 15:51
Can you please explain the above. Why || ? – Nate Pet Apr 06 '12 at 15:51
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@Nate: It's an 'or' operator, which means this: `var inf = (id if id is not undefined, otherwise use "") + "|" + (city if city is not undefined, otherwise use "")` – Elliot Bonneville Apr 06 '12 at 15:52
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@EliranMalka: This works for any value evaluating to `false`. So also `0`, which might not be wanted. – Felix Kling Apr 06 '12 at 15:54
@Nate Pet - all javascript expressions return a boolean value, thus if the check using a boolean operator (||) will be evaluated to false, the next expression will be evaluated (an empty string assignment). – Eliran Malka Apr 06 '12 at 15:54
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@EliranMalka: Careful with your wording. `1+1` returns `2` which is not a boolean value. – Felix Kling Apr 06 '12 at 15:56
@EliranMalka: Not quite. It's not that all expressions *return* a boolean, it's that all expressions can be *converted* to a boolean. – gen_Eric Apr 06 '12 at 16:03
@nickf: Without parenthesis, it's interpreted as `inf = (id) || ("" + "|" + city) || ("");` – gen_Eric Apr 06 '12 at 16:09

score 5 · Accepted Answer · answered Apr 06 '12 at 15:52

5

var inf = (id == null ? '' : id) + '|' + (city == null ? '' : city)

answered Apr 06 '12 at 15:52

Philipp

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That's just a longer way to do what Elliot is doing in his answer – nickf Apr 06 '12 at 15:54
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I have no idea why this was accepted instead of pysho's answer. – Elliot Bonneville Apr 07 '12 at 14:38
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Sometimes longer and easier to read and understand answers are better than shorter and cryptic ones. As long as it's not wrong, why do people care. – Tony_Henrich Dec 15 '17 at 01:21

score 1 · Answer 4 · answered Mar 25 '20 at 10:36

function nullToStr(str) {
    return !str || 0 === str.length ? '' : str;
}

usage:

console.log(nullToStr(null);

        function nullToStr(str) {
    return !str || 0 === str.length ? '' : str;
}

console.log(`The value which was null = ${nullToStr(null)}`);
console.log(`The value which was null = ${nullToStr(undefined)}`);
console.log(`The value which was null = ${nullToStr('')}`);
console.log(`The value which was null = ${nullToStr('asdasd')}`);

I think it will help and is much easier to use. Obviously, it is based on the other answers i found in this thread.

score 0 · Answer 5 · answered Apr 06 '12 at 15:57

0

var inf = (id && city) ? (id+"|"+city) : "";

answered Apr 06 '12 at 15:57

xdazz

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What if one or the other is null? He wanted each variable replaced with `""` if it was null, not the whole thing. – gen_Eric Apr 06 '12 at 16:00
@Rocket "if id or city are null then inf will be null", I think he wants empty string either one is null. – xdazz Apr 07 '12 at 05:41

score 0 · Answer 6 · answered Apr 06 '12 at 16:51

Equivalent to c# var inf = (id ?? "") + (city ?? ""); (if id and city are nullable) is

var inf = (id || '') + (city || '');

This is referred to as 'Short-Circuit Evaluation'. Nullability is not an issue in javascript (in js all variables are nullable), but id and city have to be assigned (but do not need a value, as in var id, city).

score 0 · Answer 7 · answered Apr 06 '12 at 16:52

0

if (id != ""){
inf = id;
if (city != ""){ inf += " | " + city ;}
}
else 
inf= city;

answered Apr 06 '12 at 16:52

ouday khaled

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javascript null value in string

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