what is the difference between != and !== in Javascript?

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Javascript === vs == : Does it matter which “equal” operator I use?

Are != and !== are respectively the same as == and ===?

score 15 · Accepted Answer · answered Jul 14 '11 at 12:36

15

!== and === are strict comparison, and == / != are loose comparison. It's best to use strict comparison.

answered Jul 14 '11 at 12:36

wanovak

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Well, i think loose comparisons are useful. – Pwnna Jul 14 '11 at 12:37
I didn't say they weren't, but if you're used to using strict comparison and only use loose when it's useful to, you're going to run into a lot less bugs (generally.) – wanovak Jul 14 '11 at 12:39
That's not a sufficient answer. Iit is better, because ... ? You are running into a lot less bugs, because ...? – JensG Feb 08 '19 at 09:34

score 6 · Answer 2 · answered Jul 14 '11 at 12:37

6

true == 1 gives you true

true === 1 gives you false

Reason is that == compares only the value (so that 1, '1' is considered as true)

=== compares the value and the type.

Same thing in PHP.

answered Jul 14 '11 at 12:37

Pwnna

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hungryMind · Answer 3 · 2011-07-14T12:48:32.150

4

== compares the value of object while === compares the object value and type.

edited Jul 14 '11 at 12:48

answered Jul 14 '11 at 12:37

hungryMind

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That would mean `[1] == [1]` and that you cannot do `1 === 1` as numbers have no reference. – pimvdb Jul 14 '11 at 12:37
by reference, i meant value & type. See edit – hungryMind Jul 14 '11 at 12:49

score 2 · Answer 4 · answered Jul 14 '11 at 12:37

yes it is.

<script>   

    var str = '1234';
    var int = parseInt('1234');

    if (int !== str)
    {
       alert('returns true and alerts');
    }

    if (int === str)
    {
       alert('returns false');
    }
</script>

http://sandbox.phpcode.eu/g/c801e.php

what is the difference between != and !== in Javascript?

4 Answers4