The function in JS

First, the way the function is defined

(1) Normal way

Syntax: function name (parameter) {

function body

}

Code:

Function method () { Alert ("TestMethod"); } Method ();

(2) anonymous function

Syntax: function (parameter) {

function body

}

Code:

var method = function () { Alert ("yyy"); }; Method ();

(3) Object functions

Syntax: new function (argument list, function body);

Note: The parameter name must be in the form of a string, and the last one is the function body and the function body needs to be in string form.

Code:

var fn = new Function ("A", "B", "Alert (a+b)"); FN (2,5);

Second, the parameters of the function

Note: (1) parameter does not have VAR modifier

(2) The format of formal parameters and arguments is not necessarily equal

(3)arguments objects are arrays that encapsulate the passed arguments

Code:

function fn (a,b,c) { var sum = a+b+c; alert (sum); Arguments is the number of arrays that encapsulate the passed arguments for (Var i=0;i<arguments.length;i++) { Alert (Arguments[i]); } } FN (1,2,4,8);

Third, the return value of the function

(1) You do not have to indicate whether you have a return value when defining a function

(2) The return value simply passes the return keyword and the return code does not execute

Code:

function fn (A, b) { return a+b; Alert ("XXXX");// The code here does not execute } Alert (FN (2,3));

Four, JS global function

Global properties and functions are available for all built-in JavaScript objects

(1) encoding and decoding

decodeURI () decodes a coded URI.

decodeURIComponent () decodes a coded URI component.

encodeURI () encodes the string as a URI.

encodeURIComponent () encodes the string as a URI component.

Escape () encodes a string

Code:

var url = "Http://www.baidu.com?name= Zhang &password=12//3"; Alert (encodeURI (URL)); Http://www.baidu.com?name=%E5%BC%A0&password=123 Alert (encodeuricomponent (URL)); Http%3a%2f%2fwww.baidu.com%3fname%3dzhangsan%26password%3d123 Alert (Escape (URL)); Http%3a//www.baidu.com%3fname%3dzhangsan%26password%3d123

(2) Forced conversion

Number () Converts the value of the object to a digit.

String () Converts the value of the object to a string.

(3) Conversion to Digital

parseint () parses a string and returns an integer.

Parsefloat () parses a string and returns a floating-point number.

(4) eval () computes the JavaScript string and executes it as script code.

Code:

var str = "var a=2;var b=3;alert (a+b)"; eval (str); function Print (str) { eval (str); } Print (" custom Logic ");

 

The function in JS