Operators - JavaScript by Example - page 96

Table 5.6 Comparison Operators (continued)

Operator/Operands Function

x >= y x is greater than or equal to y

x < y x is less than y

x <= y x is less than or equal to y

x = = = y x is identical to y in value and type

x != = y x is not identical to y

What Is Equal? In an id l wo ld, th e would be equ y b tw en the ex s and
among the races and religions, but in the real world equality is a debatable topic, often
determined by governments. In JavaScript, operators determine the equality or inequal-
ity of their operands, based on more specific rules. When using the == or != equality
operators, the operands may be of any given data type—numbers, strings, Booleans,
objects, arrays, or a combination of these—and there are rules that govern whether they
are equal. For example, two strings are equal when they have the same sequence of char-
acters, same length, and same characters in corresponding positions. Two numbers are
equal when they have the same numeric value. If a string is compared with a number,
they are equal if the number has the same characters as the string; for example, “500” is
equal to 500 . NaN (Not a Number) is not equal to anything, including NaN . Positive and
negative zeros are equal. Two objects are equal if they refer to the same object. Two Bool-
ean operands are equal if they are both true or both false . Null and undefined types are
equal. To test any of the expressions shown in Table 5.7, use the JavaScript Console. Fig-
ure 5.8 shows an example using Firefox.

Table 5.7 Equality Test with Strings and Numbers

Test Are They Equal?

"William" == "William" true

"william" == "William" false

5 == 5.0 true

"54" == 54 true

"5.4" == 5.4 true

NaN == NaN false

null == null true

-0 == +0 true