Dynamic HTML: The Definitive Reference

Name

== — NN 2 IE J1 ECMA 1

Synopsis

The equality operator. This operator compares two operand values and returns a Boolean result. The behavior of this operator differs with the version of JavaScript specified for the SCRIPT element. If the LANGUAGE attribute is set to JavaScript or JavaScript1.1, some operands are automatically converted as shown in the following table:

Left Operand	Right Operand	Description
Object reference	Object reference	Compare evaluation of object references.
Any data type	null	Convert left operand to its object type and compare against null .
Object reference	String	Convert object to string (via toString()) and compare strings.
String	Number	Convert string to a number and compare numeric values.

Version 1 of ECMAScript observes the same behavior.

The situation is a bit different in Navigator when the SCRIPT element is set to LANGUAGE="JavaScript11.2". The browser is more literal about equality, meaning that no automatic data conversions are performed. Therefore, whereas the expression:

123 == "123"

evaluates to true in most situations due to automatic data type conversion, the expression evaluates to false in Navigator 4 but only in statements belonging to explicitly JavaScript 1.2 scripts. Internet Explorer 4’s equivalent of unconverted equality comparison is the identity operator (===).

Regardless of version, if you wish to compare the values of objects (for example, strings explicitly generated with the new String() constructor), you need ...