Whats the most idiomatic way to declare a list of local javascript variables?

Question

I know all of the below versions work, and I've see them all in the wild to varying degrees. Just wondering if there is one fairly standard idiomatic way among these (are there any references to support this)?

Version (1):

var x = 1;
var y = 2;
var z = 3;

Version (2):

var x = 1,
    y = 2,
    z = 3;

Version (3):

var x = 1, y = 2, z = 3;

jslint prefers the single var statement (version 2). Crockford advocates for it. — Michael Berkowski
– Michael Berkowski, Commented Dec 2, 2011 at 19:03
(2) and (3) are the same. Or are you asking about whitespace best practices too? — Roatin Marth
– Roatin Marth, Commented Dec 2, 2011 at 19:26
@RoatinMarth, yes I was looking for most idiomatic whitespace too. — Ben Lee
– Ben Lee, Commented Dec 2, 2011 at 20:12

Matt · Accepted Answer · 2011-12-02 20:34:11Z

3

Ideally, it should be the second or third, as they prompt you to declare all your variables in the same place (i.e. at the top of the script). Word had it that it was also slighty quicker, but my JSPerf gives them the same results in IE9 and Chrome 15.

However, I find the first easier to a) read, and b) easier to maintain; it's easy to miss one ,, or forget to change the last ; to a , when you add a new variable, and you end up leaking it into the global scope.

edited Dec 2, 2011 at 20:34

answered Dec 2, 2011 at 19:27

Matt

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2 Comments

Ben Lee Over a year ago

This seems to be a clear summary of the wildly opinionated and contradictory things I've seen all over the web. Thanks!

Ben Lee Over a year ago

Interestingly, I've seen #3 advocated before, and never understood why anyone would prefer that form, but in light of your answer I have a theory. It (a) encourages all variable declarations in the same place and (b) is not likely someone will screw up the punctuation marks. So it has something each of the others has (and something each of the others lack). But I find it by far the hardest to read. So I guess they all have advantages.

tybro0103 · Accepted Answer · 2011-12-02 19:04:12Z

3

6 of one, half a dozen of another... it's all the same.

answered Dec 2, 2011 at 19:04

tybro0103

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Comments

Declan Cook · Accepted Answer · 2011-12-02 19:25:40Z

1

They are all 'valid' but I find version 2 to be the most used.

answered Dec 2, 2011 at 19:25

Declan Cook

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