Javascript [Electronic resources] : The Definitive Guide (4th Edition) نسخه متنی

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( )