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This article mainly introduces ajax how to achieve callback function parameter transfer, the article introduces in great detail, has a certain reference value, interested friends must read it!

Property methods can take parameters:

The copy code is as follows:

Function ClassX (name) {

This.name = name

ClassX.prototype.show = function (param) {

Alert (this.name + "" + param)

}

}

Var o = new ClassX ("name")

O.show ("param"); / / name param

However, although the reference is defined directly in the function signature, it may not work if it is passed through other function callbacks instead of calling o.show ('param') yourself, because others may not necessarily pass this parameter to you when calling this method, such as when using ajax

Request.onreadystatechange=function (param) {...}

Or

Request.onreadystatechange=callBack;function callBack (param) {...}

It doesn't work because ajax doesn't pass you the param parameter at all, which is something like:

The copy code is as follows:

/ / request.onreadystatechange = orgEval;// wrong practice

/ / request.onreadystatechange = function (request, pOrgName) {/ / wrong practice

/ / orgEval (request, pOrgName)

/ /}

/ /...

Request.onreadystatechange = function () {/ / correct practice

OrgEval (request, pOrgName); / / call the callback implementation in the anonymous function and pass in parameters directly. The closure property of JavaScript is used here.

}

/ /...

Function orgEval (req, orgName) {

/ /...

}

In this way, the function is implemented by calling a callback within an anonymous function and passing in parameters directly.

Callback function that ajax passes parameters to onreadystatechange

I have started to learn ajax these days, and I have the requirement of a callback function that passes parameters to XMLHttpRequest.onreadystatechange when I do the experiment page. If you baidu, you will find that there are many people talking about it. The method of search is something like this:

XmlHttp.onreadystatechange=function () {callback (aheline b);}

Two parameters, an and b, are passed.

Later, I found a method by myself, and there must be a lot of people who know it, but I didn't find it on baidu, so I wrote it down here and promoted it.

The copy code is as follows:

XmlHttp.a=a

XmlHttp.b=b

XmlHttp.onreadystatechange=callback

.

.

Function callback ()

{

If (this.readyState==4)

{

A=this.a

B=this.b

.

}

}

That is to add two properties to the xmlHttp object and call those two properties directly with this in the callback function.

In addition, a little bit of my own experience, xmlHttp had better be written as a global variable, I found at first that there are always some requests that do not achieve their goals. Later, it turns out that xmlHttp is written in a function, and when that function runs out, the xmlHttp life cycle ends. In this way, some requests are implemented before the end of the life cycle, while others are gone.

These are all the contents of the article "how to pass callback function parameters in ajax". Thank you for reading! Hope to share the content to help you, more related knowledge, welcome to follow the industry information channel!

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