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This section provides information about changes to the equality
operators and the new delete
operator.
Equality Operators
If the <SCRIPT> tag uses LANGUAGE=JavaScript1.2 , the
equality operators (== and != ) work differently. This section
describes how the equality operators work without LANGUAGE=JavaScript1.2 and
how they work with LANGUAGE=JavaScript1.2 . For instructions on writing code
to convert strings and numbers, see "Data
Conversion".
Equality Operators Without LANGUAGE=JavaScript1.2
The following describes how the equality operators (== and != )
worked in previous versions of JavaScript and how they work in JavaScript 1.2 when LANGUAGE=JavaScript1.2
is not used in the <SCRIPT> tag. Note that if LANGUAGE=JavaScript ,
and LANGUAGE=JavaScript1.1 are used, the equality operators maintain their
previous behavior.
Equality Operators With LANGUAGE=JavaScript1.2
If LANGUAGE=JavaScript1.2 is used in the <SCRIPT> tag,
the equality operators (== and != ) behave as follows:
This approach avoids errors, maintains transitivity, and simplifies the language.
Data Conversion
To write JavaScript code that converts strings to numbers and numbers to strings in the
different versions of Navigator, follow these guidelines:
When writing for all versions of Navigator:
- To convert x to a string, use " " + x. For example,
"" + 3 == "3"
- To convert x to a number, use (x - 0). For example,
"3" - 0 == 3
- To convert x to a Boolean, use !!x. For example,
!!null == false
When writing for Navigator 4.0 only:
- To convert x to a string, in addition to " " + x, you can use String(x). For
example,
var x = 3
String(x) = "3"
- To convert x to a number, in addition to (x - 0), you can use Number(x). For example,
var x = "3"
Number(x) = 3
- To convert x to a Boolean, in addition to !!x, you can use Boolean(x). For example,
var x = null
Boolean(x) = false
Example
The following example demonstrates the == operator with different <SCRIPT>
tags.
delete
Core operator. Deletes an object's property or an element at a specified index in an
array.
Syntax
delete objectName.property
delete objectname[index]
delete property
Parameters
property is an existing property. (The third form is legal only within a with
statement.)
index is an integer representing the location of an
element in an array.
Description
If the deletion succeeds, the delete operator sets the property or element to undefined .
delete always returns undefined.
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