Availability

JavaScript 1.0; JScript 1.0; ECMAScript v1

Synopsis

parseFloat(s)

Arguments

s

The string to be parsed and converted to a number.

Returns

The parsed number, or NaN if s does not begin with a valid number. In JavaScript 1.0, parseFloat( ) returns 0 instead of NaN when s cannot be parsed as a number.

Description

parseFloat( ) parses and returns the first number that occurs in s. Parsing stops, and the value is returned, when parseFloat( ) encounters a character in s that is not a valid part of the number. If s does not begin with a number that parseFloat( ) can parse, the function the not-a-number value NaN. Test for this return value with the isNaN( ) function. If you want to parse only the integer portion of a number, use parseInt( ) instead of parseFloat( ).

Bugs

NaN is not supported in JavaScript 1.0, so in that version of the language, parseFloat( ) returns 0 when it cannot parse s. This means that in JavaScript 1.0, if the return value of parseFloat( ) is 0, you must perform additional tests on s to determine whether it really represents the number zero or does not represent a number at all.

See Also

isNaN( ), parseInt( )