Equal and Not Equal

The equal operator in JavaScript is ==. The not-equal operator is !=.

Rules for the equal and not-equal operators:

Expression	Value
null == undefined	true
null == any other value	false
undefined == any other value	false
NaN == any other value	false
NaN != NaN	true
false == 0	true (false converts to 0, true converts to 1)
true == 1	true (false converts to 0, true converts to 1)
true == 2	false (false converts to 0, true converts to 1)
undefined == 0	false
null == 0	false
"5" == 5	true

If one operand is a string and the other is a number, the string is converted into a number. If only one of the operands is an object, the valueOf() is called on the object to get a primitive value. If both operands are objects and they are the same object, the equal operator is used.

 
<!DOCTYPE HTML>
<html>
<head>
<title>Example</title>
</head>
<body>
  <script type="text/javascript">
    var firstVal = 5;
    var secondVal = "5";
    if (firstVal == secondVal) {
      document.writeln("They are the same");
    } else {
      document.writeln("They are NOT the same");
    }
  </script>
</body>
</html>

Click to view the demo