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The JavaScript FAQ
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Converting Strings to Numbers

Question: How do I convert strings to numbers in JavaScript?

Answer: To convert a string to a number, use the JavaScript function parseFloat (for conversion to a floating-point number) or parseInt (for conversion to an integer).

parseFloat syntax:   parseFloat('string')

How it works:
The argument of parseFloat must be a string or a string expression. The result of parseFloat is the number whose decimal representation was contained in that string (or the number found in the beginning of the string). If the string argument cannot be parsed as a decimal number, the results will be different in different browsers (either 0 or NaN).

Examples (comments in each line give the conversion results):

parseFloat('1.45kg')  // 1.45
parseFloat('77.3')    // 77.3
parseFloat('077.3')   // 77.3
parseFloat('0x77.3')  // 0
parseFloat('.3')      // 0.3
parseFloat('0.1e6')   // 100000

parseInt syntax:   parseInt( 'string' [, base] )

How it works:
The first argument of parseInt must be a string or a string expression. The result returned by parseInt is an integer whose representation was contained in that string (or the integer found in the beginning of the string). The second argument (base), if present, specifies the base (radix) of the number whose string representation is contained in the string. The base argument can be any integer from 2 to 36.

If there is only one argument, the number base is detected according to the general JavaScript syntax for numbers. Strings that begin with 0x or -0x are parsed as hexadecimals; strings that begin with 0 or -0 are parsed as octal numbers. All other strings are parsed as decimal numbers.

If the string argument cannot be parsed as an integer, the results will be different in different browsers (either 0 or NaN).

Examples (comments in each line give the conversion results):

parseInt('123.45')  // 123
parseInt('77')      // 77
parseInt('077',10)  // 77
parseInt('77',8)    // 63  (= 7 + 7*8)
parseInt('077')     // 63  (= 7 + 7*8)
parseInt('77',16)   // 119 (= 7 + 7*16)
parseInt('0x77')    // 119 (= 7 + 7*16)
parseInt('099')     // 0 (9 is not an octal digit)
parseInt('99',8)    // 0 or NaN, depending on the platform
parseInt('0.1e6')   // 0
parseInt('ZZ',36)   // 1295 (= 35 + 35*36)

JavaScripter.net. Copyright © 1999-2006, Alexei Kourbatov

The JavaScript FAQ
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