Operators - JavaScript by Example - page 97

Table 5.7 Equality Test with Strings and Numbers (continued)

Test Are They Equal?

false == false true

true == 1 true

null == undefined true

Figure 5.8 Testing the equality of two strings. Is "William" equal to "william" ? Nope.

What Is Identical? Men are equal; clones are identical. The === and !== equality
operators test that its operands are not only of the same value, but also of the same data
type. String “54” is equal to number 54 , but not identical because one is a string and the
other is a number, even though their values are equal. See Table 5.8.

Table 5.8 Identity Test with Strings and Numbers

Test Are They Identical?

"William" === "William" true

"william" === "William" false

5 === 5.0 true

"54" === 54 false

NaN === NaN false

null === null true

-0 === +0 true

false === false true

true === 1 false

null === undefined false