CODEWITHSUNDEEP
javascriptcomparison-operatorsequality-operatoridentity-operator
Shiva
Shiva

Reputation: 18275

Difference between == and === in JavaScript

What is the difference between == and === in JavaScript? I have also seen != and !== operators. Are there more such operators?

Upvotes: 1711

Views: 1049587

Answers (2)

Jack Sleight
Jack Sleight

Reputation: 17118

=== and !== are strict comparison operators:

JavaScript has both strict and type-converting equality comparison. For strict equality the objects being compared must have the same type and:

  • Two strings are strictly equal when they have the same sequence of characters, same length, and same characters in corresponding positions.
  • Two numbers are strictly equal when they are numerically equal (have the same number value). NaN is not equal to anything, including NaN. Positive and negative zeros are equal to one another.
  • Two Boolean operands are strictly equal if both are true or both are false.
  • Two objects are strictly equal if they refer to the same Object.
  • Null and Undefined types are == (but not ===). [I.e. (Null==Undefined) is true but (Null===Undefined) is false]

Comparison Operators - MDC

Upvotes: 1209

sdfx
sdfx

Reputation: 21713

Take a look here: http://longgoldenears.blogspot.com/2007/09/triple-equals-in-javascript.html

The 3 equal signs mean "equality without type coercion". Using the triple equals, the values must be equal in type as well.

0 == false   // true
0 === false  // false, because they are of a different type
1 == "1"     // true, automatic type conversion for value only
1 === "1"    // false, because they are of a different type
null == undefined // true
null === undefined // false
'0' == false // true
'0' === false // false

Upvotes: 2038

Related Questions