AJAX - The Complete Reference

558 Part IV: Appendixes

Method Explanation Example

parseInt("string",

[radix])

Converts a string value to an

integer number if possible. If no

number is found in the string

passed or another non-number

type is used, it returns NaN.

The optional radix value can be

set to the base of the desired

conversion. This may be

important if converting from

a leading zero-valued string,

which would be in octal.

var a=parseInt("5");

// 5

var b=parseInt("5.21");

// 5

var c=parseInt("5tom");

// 5

var d=parseInt("true");

// NaN

var e=parseInt(window);

// NaN

parseFloat("string") Converts string value into

a floating point number if

possible. When passed non-

strings or if no floating point is

found in the passed string, it

returns NaN.

var x = parseFloat("3.15 ");

// x = 3.15

var y =

parseFloat("74.5red-dog ";

// y = 74.5

var z = parseFloat("TAP ");

// z = NaN

var q = parseFloat(window);

// q = NaN

+ value Converts value into number if

possible, given type conversion

required for prefix plus operator.

var x = + "39";

Number(value) Converts value into a number if

possible, otherwise NaN.

var x = Number(5);

var y = Number("5"); //5

var z = Number("F"); //NaN

String(value) Constructor that turns the

passed value into a string type.

var x = String(true);

var y = String(5); //"5"

Boolean(value) Constructor that turns the

passed value into a Boolean

type.

var x = Boolean(true);

var y = Boolean(1); /* true

*/

var z = Boolean("");/* false

*/

!!value Converts value to its Boolean

representation because of

implicit convert of! operator.

var x = !!(true);

var y = !!(1); // true

var z = !!""; // false

Obj.valueOf() The method that is called to

convert an object to a primitive

value. Rarely called directly.

alert(window.valueOf());

Obj.toString() A method to present an object

in a string form. Similar to

valueOf() though often

overridden by developers.

alert(window.toString());

TABLE A-7 Type Conversion Methods