Assign two variables to the same value with one expression?

Question

Is there any way to assign two variables to the same value?

Just tried this:

let x, y = 'hi'

and it's compiling to this:

'use strict';

var x = void 0,
    y = 'hi';

`let x = 'hi', y = x;` - that's the only way to do that in a single statement. — zerkms, May 09 '16 at 05:23

Dmitri Pavlutin · Accepted Answer · 2016-05-09T05:52:08.043

7

Yes, it is possible:

let x, y;
x = y = 'hi';

It is called chaining assignment, making possible to assign a single value to multiple variables.
See more details about assignment operator.

If you have more than 2 variables, it's possible to use the array destructing assignment:

let [w, x, y, z] = Array(4).fill('hi');

edited May 09 '16 at 05:52

answered May 09 '16 at 05:18

Dmitri Pavlutin

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zerkms · Answer 2 · 2016-05-09T05:45:16.823

7

There is absolutely no reason to prefer the destructuring assignment over simply

let x = 'hi', y = x;

Not only it's one statement instead of two, but it also avoids extra allocations (the provided solution with destructuring allocates at least one object with no good reason).

edited May 09 '16 at 05:45

answered May 09 '16 at 05:35

zerkms

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Ok, but what about 5 variables? `let x = 'hi', a = x, b = x, c = x, d = x`. Too hard to read. – Dmitri Pavlutin May 09 '16 at 05:37
1

@DmitriPavlutin just don't write code that requires you to create 5 identical variables (it looks awkward in the very first place) – zerkms May 09 '16 at 05:38
2

@zerkms I think you meant to say "There is absolutely no reason to prefer _the destructuring assignment_ to `let x = 'hi', y = x;`" – Soubhik Mondal May 09 '16 at 05:44
@BlazeSahlzen yep thanks. – zerkms May 09 '16 at 05:45

score 1 · Answer 3 · 2016-05-09T05:21:55.190

1

You can do this way .. But my suggest try to avoid it.

var one, two, three;
one = two = three = "";

edited May 09 '16 at 05:21

answered May 09 '16 at 05:19

JS by itself doesn't use explicitly defined types such as string. – Satej S May 09 '16 at 05:20
Why should I avoid it? – May 09 '16 at 05:53
@torazaburo because it's a strong positive sign that you're doing something wrong. Just create one variable, not 3 with the same data. – zerkms May 09 '16 at 05:58
Huh? What if I have two or three distinct variables, that I happen to want to initialize to the same value? – May 09 '16 at 06:30
@torazaburo I don't remember last time I did that. Any chance you can make of an algorithm/a task where it's the mandatory implementation detail? – zerkms May 09 '16 at 07:13
1

I don't really care, and it's a semi-stupid question, but yes, I can easily imagine cases where I have two counters, let's say, and want to initialize them both to zero. However, I see no reason not to just say `var x=0, y=0;`. – May 09 '16 at 16:05

score 0 · Answer 4 · answered May 09 '16 at 05:20

0

That's expected behavior. From the EMCA-262 6th edition:

If a LexicalBinding in a let declaration does not have an Initializer the variable is assigned the value undefined when the LexicalBinding is evaluated.

answered May 09 '16 at 05:20

uh oh somebody needs a pupper

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score -2 · Answer 5 · answered May 09 '16 at 05:27

-2

var x = y = 'hi';
alert('x'+x);
alert('y'+y);

Fiddle

answered May 09 '16 at 05:27

Imad

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Assign two variables to the same value with one expression?

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