JavaScript parseInt() Function

Definition and Usage

The parseInt() function parses a string and returns an integer.
The radix parameter is used to specify which numeral system to be used, for example, a radix of 16 (hexadecimal) indicates that the number in the string should be parsed from a hexadecimal number to a decimal number.
If the radix parameter is omitted, JavaScript assumes the following:

• If the string begins with "0x", the radix is 16 (hexadecimal)
• If the string begins with "0", the radix is 8 (octal). This feature is deprecated
• If the string begins with any other value, the radix is 10 (decimal)

Syntax

parseInt(string, radix)

Parameter	Description
string	Required. The string to be parsed
radix	Optional. A number (from 2 to 36) that represents the numeral system to be used

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Tips and Notes

Note: Only the first number in the string is returned!
Note: Leading and trailing spaces are allowed.
Note: If the first character cannot be converted to a number, parseInt() returns NaN.

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Example

In this example we will use parseInt() to parse different strings:

<script type="text/javascript"> document.write(parseInt("10") + "<br />"); document.write(parseInt("10.00") + "<br />"); document.write(parseInt("10.33") + "<br />"); document.write(parseInt("34 45 66") + "<br />"); document.write(parseInt(" 60 ") + "<br />"); document.write(parseInt("40 years") + "<br />"); document.write(parseInt("He was 40") + "<br />"); document.write("<br />"); document.write(parseInt("10")+ "<br />"); document.write(parseInt("10",10)+ "<br />"); document.write(parseInt("010")+ "<br />"); document.write(parseInt("10",8)+ "<br />"); document.write(parseInt("0x10")+ "<br />"); document.write(parseInt("10",16)+ "<br />"); </script>

The output of the code above will be:

10 10 10 34 60 40 NaN 10 10 8 8 16 16