Example of setting default parameter values in JavaScript _javascript tips

First type:

function test (a,b) {

var a = Arguments[0]? arguments[0]: 1;//Setting the default value of parameter A is 1

var b = arguments[1]? arguments[1]: 9; The default value for setting parameter B is 9 return

a+b;

It is equivalent to

function test () {

var a = Arguments[0]? arguments[0]: 1;//Setting the default value of parameter A is 1

var b = arguments[1]? arguments[1]: 9;// The default value for parameter B is 9 return

a+b;

Call Example

Alert (test ()); Output

alert (Test (5));//Output

alert (test (5,6));//Output One

alert (test (null,6));//Output 7

alert ( 6,null)); Output 15

The second type:

function test (blog,address) {

blog=blog| | ' Forgotten ~ Shallow thinking ';

address=address| | ' Www.jb51.net ';

Alert (' Blog name is ' +blog+ ' address is ' +address ');

}

It is equivalent to

function test (blog,address) {

if (!blog) {blog= ' forgotten ~ shallow thinking ';}

if (!address) {address= ' www.jb51.net ';}

Alert (' Blog name is ' +blog+ ' address is ' +address ');

}

Call Example

Test (); Blog name is forgotten ~ The address is www.jb51.net

test (' csdn ', ' blog.csdn.net ');//Blog name is CSDN address is blog.csdn.net

test (', ' blog.csdn.net/u011043843 '); Blog name is forgotten ~ Shallow thinking

The third type:

function test (setting) {

var defaultsetting={

name: ' Program Enthusiast ', Age

: ' 1 ',

Phone: ' 15602277510 ',

QQ: ' 259280570 ', message

: ' Welcome you to join '

};

$.extend (defaultsetting,setting);

var msg= ' name: ' +defaultsetting.name

+ ', Age: ' +defaultsetting.age

+ ', tel: ' +defaultsetting.phone

+ ', QQ group: ' +defaultsetting.qq

+ ', Description: ' +defaultsetting.message

+ '. ';
Alert (msg);
}

Call Example

Test (); Output: Name: Program enthusiasts, Age: 1, Tel: 15602277510,qq Group: 259280570, Description: welcome you to join.

Test ({

name: ' Dwqs ', Age: ' m

',

QQ: ' 461147874 ', message

: ' Blog: www.jb51.net '

});

Output: Dwqs, Age: 20, Tel: 15602277510,qq Group: 461147874, Description: Blog: www.jb51.net.

PS: The function parameters are relatively long, you can use this method. This is an extension of jquery, so you need to introduce jquery.