What is exactly the meaning of “===” in javascript? [duplicate]

Answer 1

The === operator means "is exactly equal to," matching by both value and data type.

The == operator means "is equal to," matching by value only.

Answer 2

Ripped from my blog: keithdonegan.com

The Equality Operator (==)

The equality operator (==) checks whether two operands are the same and returns true if they are the same and false if they are different.

The Identity Operator (===)

The identity operator checks whether two operands are “identical”.

These rules determine whether two values are identical:

• They have to have the same type.
• If number values have the same value they are identical, unless one or both are NaN.
• If string values have the same value they are identical, unless the strings differ in length or content.
• If both values refer to the same object, array or function they are identical.
• If both values are null or undefined they are identical.

Answer 3

'===' means equality without type coersion. In other words, if using the triple equals, the values must be equal in type as well.

e.g.

0==false   // true
0===false  // false, because they are of a different type
1=="1"     // true, auto type coersion
1==="1"    // false, because they are of a different type

Source: http://longgoldenears.blogspot.com/2007/09/triple-equals-in-javascript.html

Answer 4

It tests exact equality of both value and type.

given the assignment
x = 7

x===7 is true
x==="7" is false

Answer 5

In a nutshell "===" tests for the equality of value AND of type: From here: