Triple (3) Equal Signs

Question

Possible Duplicate:
JavaScript === vs == : Does it matter which “equal” operator I use?

I asked another question here and received a great answer as follows:

$(document).on("keydown", function (e) {
  if (e.which === 8 && !$(e.target).is("input, textarea") || $(e.target).is('[readonly]')) {
      e.preventDefault();
  }
});

Notice the three equal signs === in the if-statement. I have always thought you only needed two equal signs == for a javascript/jQuery if-statement. Is there any reason for the three?

UPDATE

Sorry for the duplicate question - I searched but didn't find any good questions. I guess I was using the wrong search terms.

I am guessing its checking absolute equality. Meaning, not just equal, but the same — Grigor, Jun 27 '12 at 20:47
This other question has a lot of information on the subject (http://stackoverflow.com/questions/359494/javascript-vs-does-it-matter-which-equal-operator-i-use) — MrOBrian, Jun 27 '12 at 20:48
Stack Overflow's search feature cannot handle characters such as `=`, unfortunately. But Google does work: http://www.google.com/search?q=site:stackoverflow.com+javascript+%3D%3D%3D+vs+%3D%3D — Rob W, Jun 27 '12 at 20:48

score 78 · Accepted Answer · edited Sep 27 '22 at 15:21

78

The triple equal sign in javascript means equality without type coercion.

For example:

1=="1"     // true, automatic type coercion
1==="1"    // false, not the same type.

edited Sep 27 '22 at 15:21

reza

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answered Jun 27 '12 at 20:48

Jeshurun

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JS true, false and equal in details: https://gist.github.com/romankierzkowski/9024908 – RKI Feb 16 '14 at 03:21
+1 I think in terms of strongly typed languages - so the second example would throw an error. Still not used to this and been using javascript for a while now – Radmation Sep 12 '17 at 18:48

score 14 · Answer 2 · answered Jun 27 '12 at 20:47

14

Three equal signs indicates both the value and type are equal.

answered Jun 27 '12 at 20:47

Justin

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I started to answer just like that, then figured this had to be a dupe, see [this](http://stackoverflow.com/questions/359494/javascript-vs-does-it-matter-which-equal-operator-i-use) – TecBrat Jun 27 '12 at 20:48

Triple (3) Equal Signs

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