Number() function

The Number() function performs conversions based on these rules:

Parameter	Number Function Returns
Boolean true	1
Boolean false	0
null	0
undefined	NaN
Empty string("")	0
String with only number, for example "123"	123
String with only number and plus sign, for example "+123"	123
String with only number and minus sign, for example "-123"	-123
Leading zeros are ignored, for example "0123"	123
Leading zeros are ignored, for example "+0123"	123
Leading zeros are ignored, for example "-0123"	-123
String with valid floating-point format, such as "1.1"	1.1
String with valid floating-point format, such as "+1.1"	1.1
String with valid floating-point format, such as "-1.1"	-1.1
Leading zeros are ignored, such as "01.1"	1.1
String with hexadecimal format, "0xf"	15
String with hexadecimal format, "-0xf"	-15
String with not a number value, for example "asdf"	NaN
objects	the valueOf() method is called and the returned value is converted

 
<!DOCTYPE html>
<html>
<head>
    <title>Number Example</title>
    <script type="text/javascript">
        document.writeln(Number("-123"));   //-123
        document.writeln(Number("+123"));   //123
        document.writeln(Number("-0123"));  //-123
        document.writeln(Number("0xf"));    //15
        document.writeln(Number("-0xf"));   //-15
        document.writeln(Number("asdf"));   // NaN
    </script>
</head>
<body>
</body>
</html>

Click to view the demo