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
– Felix Kling, Commented Apr 6, 2012 at 15:52
possible duplicate of null coalescing operator for javascript? — user1106925
– user1106925, Commented Apr 6, 2012 at 16:26

psyho · Accepted Answer · 2012-04-06 16:08:19Z

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 6, 2012 at 16:08

answered Apr 6, 2012 at 15:48

psyho

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3 Comments

Engineer Over a year ago

inf will not be blank , if id and city are nulls.

gen_Eric Over a year ago

@Engineer: Yes, it'll be "|", the desired result.

Engineer Over a year ago

@Rocket I know about "|", just read if id or city are null then inf will be null. of @Nate.

Elliot Bonneville · Accepted Answer · 2012-04-06 15:47:13Z

16

Total long shot, but try this:

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

answered Apr 6, 2012 at 15:47

Elliot Bonneville

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13 Comments

gen_Eric Over a year ago

I'd suggest adding parenthesis: var inf = (id || "") + "|" + (city || "");

nickf Over a year ago

@ElliotBonneville it doesn't actually matter to the interpreter (since it's equivalent), but it will matter to your co-workers.

NullUserException Over a year ago

@nickf It does make a difference. Try it.

Elliot Bonneville Over a year ago

@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 "")

Felix Kling Over a year ago

@EliranMalka: This works for any value evaluating to false. So also 0, which might not be wanted.

|

Philipp · Accepted Answer · 2012-04-06 15:52:39Z

5

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

answered Apr 6, 2012 at 15:52

Philipp

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3 Comments

nickf Over a year ago

That's just a longer way to do what Elliot is doing in his answer

Elliot Bonneville Over a year ago

I have no idea why this was accepted instead of pysho's answer.

Tony_Henrich Over a year ago

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.

Steve Johnson · Accepted Answer · 2020-03-25 10:36:37Z

1

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.

answered Mar 25, 2020 at 10:36

Steve Johnson

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Comments

xdazz · Accepted Answer · 2012-04-06 15:57:58Z

0

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

answered Apr 6, 2012 at 15:57

xdazz

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2 Comments

gen_Eric Over a year ago

What if one or the other is null? He wanted each variable replaced with "" if it was null, not the whole thing.

xdazz Over a year ago

@Rocket "if id or city are null then inf will be null", I think he wants empty string either one is null.

KooiInc · Accepted Answer · 2012-04-06 16:51:43Z

0

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).

answered Apr 6, 2012 at 16:51

KooiInc

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Comments

ouday khaled · Accepted Answer · 2012-04-06 16:52:01Z

0

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

answered Apr 6, 2012 at 16:52

ouday khaled

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