what is the meaning of "===" in javascript?

Question

I have seen many uses of "===" in conditional statements.

Can anyone tell me what does it mean?

something like ternary operator?

if(typeof(x) == "string")
{
    x= (x=== "true");
}

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comparison_Operators — Denys Séguret, Aug 23 '13 at 12:21
Means that both the value and implicit data type are the same. — The Marlboro Man, Aug 23 '13 at 12:21
@deceze, cute but the OP could easily find the answer at the link I provided or simple Google search. So will this be another case of a question easily sought out in programming documentation that tallies hundreds of upvotes for answers? Good grief... — lurker, Aug 23 '13 at 12:22
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comparison_Operators — Aashray, Aug 23 '13 at 12:23
I'm not saying W3S is particularly wrong in this case, just that one should not regard it as a primary source of knowledge! Many newbs don't know that. — deceze, Aug 23 '13 at 12:24
Read This Tutorial http://www.2ality.com/2011/06/javascript-equality.html — Butani Vijay, Aug 23 '13 at 12:29

Kevin Bowersox · Accepted Answer · 2013-08-23T12:29:58.333

The === operator checks for equality which means that the type and value are the same. The == operator checks for equivalence which means that the value is the same and it disregards the type.

Example

alert("1" == 1); //alerts true
alert("1" === 1); //alerts false, types are different.
alert(1 === 1); //alerts true

This can be useful in Javascript due to the loosely typed nature of the language and the truthy/falsey nature of variables.

For example, an empty String is == false

("") ? alert(true): alert(false); //alerts false

You will also find that 0 is == false

(0) ? alert(true): alert(false); //alerts false

As well as an empty property on an object:

({}.prop) ? alert(true): alert(false); //alerts false

In these situations it may be necessary to use the === operator when type is important.

score 2 · Answer 2 · answered Aug 23 '13 at 12:23

2

It's strict equality comparison. It means that not just the value is evaluated but also the type of the objects. More info is available in the ECMAScript-specification.

answered Aug 23 '13 at 12:23

Karl-Johan Sjögren

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score 0 · Answer 3 · answered Aug 23 '13 at 12:21

0

The === mean "equality without type coercion". Using the triple equals both the values and their types must be equal.

answered Aug 23 '13 at 12:21

federico-t

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score 0 · Answer 4 · answered Aug 23 '13 at 12:23

0

"===" does not perform type conversion so it could have a different result than "==".

answered Aug 23 '13 at 12:23

waterplea

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You mean type checking, instead of type conversion ? – Aazim Nov 06 '19 at 19:21
No, I mean type conversion. `==` converts types so it can compare them, `===` does not do that and compare as is. Therefore `'' == false` is `true` whereas `'' === false` is `false` – waterplea Nov 11 '19 at 16:30

score 0 · Answer 5 · answered Aug 23 '13 at 12:44

0

The identity (===) operator behaves identically to the equality (==) operator except no type conversion is done, and the types must be the same to be considered equal.

answered Aug 23 '13 at 12:44

Arpan Buch

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what is the meaning of "===" in javascript?

5 Answers5