Use apply to allow the javascript function to execute the Code only once.

Copy codeThe Code is as follows:
Var obj = new Object ();
Obj. triggerOnce = function (fn) {// control the function to be triggered only once
Return function (){
Try {
Fn. apply (this, arguments );
}
Catch (e ){
Var txt = "There was an error on this page. \ n ";
Txt + = "Error message:" + e. message + "\ n ";
Txt + = "Error name:" + e. name + "\ n ";
// Alert (txt); // comment out this line on the official Platform
}
Finally {
Fn = null;
}
}
}

Call form:
Copy codeThe Code is as follows:
Function showMsg (arg ){
Alert (arg );
}
Var fn = obj. triggerOnce (showMsg );
Fn (1); // only run once
Fn (2); // fn is not called

Finally, you can refer to the old article for the javascript apply method.
[Additional] use javascript to obtain the querystring Value
In common websites, "XXXX. aspx? Username = jeffwong & address = Beijing ". It is easy to get the key value through the Request object of asp.net, and it is not difficult to get the key value through js. You can use the following function to solve the problem:
Code
Copy codeThe Code is as follows:
Var urlStrs = location. search; // QueryString
Var Request = {};
Request. Count = 0;
Request. Add = function (name, value ){
If (Request. hasOwnProperty (name) = false ){
Request. Count ++; // if not, add 1 to the Count
}
Request [name] = value;
Return true;
}
Request. QueryString = function (name) {// obtain the corresponding key value
Var key = name. toString (). toLocaleLowerCase (); // case insensitive
Var result = null;
Try {
// If (Request. hasOwnProperty (key )){
Result = Request [key];
//}
}
Catch (e ){
// Alert (e. message );
}
Return result;
}
Request. Init = function (urlQueryString ){
If (urlQueryString. indexOf ("? ")! =-1 ){
Var url = urlQueryString. substr (1)
Var strArr = url. split ("&");
For (var I = 0; I <strArr. length; I ++ ){
Var strChildArr = strArr [I]. split ("= ");
Var name = String (strChildArr [0]). toLowerCase ();
Var value = unescape (strChildArr [1]); // scape Decoding
This. Add (name, value); // Add
}
}
}

The test function is as follows:
Code
Copy codeThe Code is as follows:
// Test the Function
Function test (){
Request. Init (urlStrs); // initialize the request
Alert (Request. Count );
Var name = "username ";
Var value = Request. QueryString (name );
Alert (Request [name]);
Alert (Request. QueryString (name ));
Name = "address"
Alert (Request [name]);
Alert (Request. QueryString (name ));
Name = "age ";
Alert (Request [name]);
Alert (Request. QueryString (name ));
}

It should be noted that the parameters in the url are usually encoded. This article uses the commonly used unescape for decoding. In fact, the url parameter encoding usually involves escape, encodeURIComponent and encodeURI encoding functions. escape is a built-in function of the window object, while the other two are built-in functions of javascript, their decoded functions also have a one-to-one correspondence relationship (you can refer to this article). Their Respective inversion functions are unescape, decodeURIComponent, and decodeURI.
Author: Jeff Wong