MSDN Library

Comparison Operators (JavaScript)

Returns a Boolean value indicating the result of the comparison.

expression1 comparisonoperator expression2


Any expression.


Any comparison operator.


Any expression.

When comparing strings, JavaScript uses the Unicode character value of the string expression.

The following describes how the different groups of operators behave depending on the types and values of expression1 and expression2:

Relational (<, >, <=, >=)

  • Attempt to convert both expression1 and expression2 into numbers.

  • If both expressions are strings, do a lexicographical string comparison.

  • If either expression is NaN, return false.

  • Negative zero equals Positive zero.

  • Negative Infinity is less than everything including itself.

  • Positive Infinity is greater than everything including itself.

Equality (==, !=)

  • If the types of the two expressions are different, attempt to convert them to string, number, or Boolean.

  • NaN is not equal to anything including itself.

  • Negative zero equals positive zero.

  • null equals both null and undefined.

  • Values are considered equal if they are identical strings, numerically equivalent numbers, the same object, identical Boolean values, or (if different types) they can be coerced into one of these situations.

  • Every other comparison is considered unequal.

Identity (===, !==)

These operators behave identically to the equality operators except no type conversion is done, and the types must be the same to be considered equal.

Supported in the following document modes: Quirks, Internet Explorer 6 standards, Internet Explorer 7 standards, Internet Explorer 8 standards, Internet Explorer 9 standards. See Version Information.

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