What is array literal notation in javascript and when should you use it?

Question

JSLint is giving me this error:

Problem at line 11 character 33: Use the array literal notation [].

var myArray = new Array();

What is array literal notation and why does it want me to use it instead?

It shows here that new Array(); should work fine... is there something I'm missing?

This is similar to, but not quite the same as: http://stackoverflow.com/questions/931872/whats-the-difference-between-array-and-while-declaring-a-javascript-arr/ — Borgar, Jul 07 '09 at 22:41
duplicate of [What's wrong with var x = new Array();](http://stackoverflow.com/questions/885156/whats-wrong-with-var-x-new-array) — Bergi, Jun 27 '12 at 18:07
Also always use the literal when you can because the Array constructor ( new Array() ) doesn’t always work properly. e.g. if there is a single value that is a number. > new Array(3, 11, 8) [ 3, 11, 8 ] > new Array(3) [ , , ,] > new Array(3.1) RangeError: Invalid array length — Ingadi, Dec 20 '17 at 14:59

score 102 · Accepted Answer · edited May 23 '17 at 11:47

102

array literal notation is where you define a new array using just empty brackets. In your example:

var myArray = [];

It is the "new" way of defining arrays, and I suppose it is shorter/cleaner.

The examples below explain the difference between them:

var a = [],            // these are the same
    b = new Array(),   // a and b are arrays with length 0

    c = ['foo', 'bar'],           // these are the same
    d = new Array('foo', 'bar'),  // c and d are arrays with 2 strings

    // these are different:
    e = [3],             // e.length == 1, e[0] == 3
    f = new Array(3);   // f.length == 3, f[0] == undefined

Reference: What’s the difference between “Array()” and “[]” while declaring a JavaScript array?

edited May 23 '17 at 11:47

Community

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answered Jul 07 '09 at 20:38

CookieOfFortune

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It is the "new" way...no pun intended? – arxpoetica Mar 25 '12 at 17:40
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But the answer doesn't explain that when we should use literal i.e.[] and when to use new Array(); – Dattatray Walunj Oct 08 '13 at 10:53
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Always use the literal `[]`. The reason this is better is that it's safer because someone could potentially overwrite the `window.Array` constructor but not the literal. – thwd Nov 07 '14 at 19:12
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For those using TypeScript, the equivalent is `var a: string[] = [];`. – teuber789 Oct 18 '19 at 03:19

score 23 · Answer 2 · edited May 23 '17 at 11:54

See also: What’s wrong with var x = new Array();

Aside from the Crockford argument, I believe it is also due to the fact that other languages have similar data structures that happen to use the same syntax; for example, Python has lists and dictionaries; see the following examples:

// this is a Python list
a = [66.25, 333, 333, 1, 1234.5]

// this is a Python dictionary
tel = {'jack': 4098, 'sape': 4139}

Isn't it neat how Python is also grammatically correct Javascript? (yes, the ending semi-colons are missing, but those aren't required for Javascript, either)

Thus, by reusing common paradigms in programming, we save everyone from having to relearn something that shouldn't have to.

Thanks for the explanation. Great answer! – Evik James Sep 05 '12 at 16:40 — Evik James, Sep 05 '12 at 16:40

score 3 · Answer 3 · edited Jan 22 '15 at 13:28

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Aside from the Crockford argument, jsPerf says that it's faster. http://jsperf.com/new-vs-literal-array-declaration

edited Jan 22 '15 at 13:28

Useless Code

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answered Jan 04 '14 at 06:29

ecMode

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score 0 · Answer 4 · answered Apr 25 '14 at 14:22

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After looking at @ecMode jsperf, I did some further tests.

When using push to add to the array new Array() is considerably faster on Chrome:

http://jsperf.com/new-vs-literal-array-declaration/2

Using index to add is slightly faster for [].

answered Apr 25 '14 at 14:22

Skeep

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What is array literal notation in javascript and when should you use it?

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