Web Standards Programmer's Reference: HTML, CSS, JavaScript®, Perl, Python®, and PHP

20.6. Built-in Functions

JavaScript provides a few built-in functions for data manipulation. Most of the built-in functions exist to convert data between the various data types and to check if data is of a particular type. The following table lists the supported functions:

Function	Use	Returns
escape	Creates portable data — typically used to encode URLs and other information that may, but generally should not, include extended characters. Extended characters (non-alphanumeric) are replaced by their ASCII number equivalent in hexadecimal %xx form. For example, a space (ASCII 32) becomes %20.	Encoded version of supplied argument.
eval	Parses the supplied string for JavaScript code and executes the code if found.	The value of the last valid statement or expression encountered in the supplied argument.
isFinite	Tests an expression or variable to see if it is a valid number.	True if the supplied argument is a valid number, false if the supplied argument is not a valid number.
isNaN	Tests an expression or variable to see if it is not a (valid) number.	Returns true if the argument is not a number and false if the argument is a number.
number	Converts an object (typically string data) to a number.	Returns the supplied argument converted to a number or the value NaN (not a number) if the argument cannot be converted to a valid number.
parseFloat	Parses the given argument for a valid floating-point number. Parsing begins with the first character and ends with the first character that cannot be converted. ...