Question

我创建了一个版本，其中包含与我的问题相关的所有内容：

//new version doesn't work ->

function global_function(server_response){}

function Constructor(global_function){
    this.local_reference_to_global_function=global_function;}
Constructor.prototype.api_function(){
    //this.localreference_to_global_function("test"); // works
    //global_function("test"); // works
    xmlhttp=XMLHttpRequest();
    xmlhttp.onreadystatechange=function(){
        this.local_reference_to_global_function(xmlhttp.responseText)} 
        // does not work on asynchronuous callback
        // probably scope/visibility/closure lifetime/whatever is wrong
        // and I need to understand what is wrong to fix it in my code .
        // firebug said that "this.local_reference_to_global_function is not a function"
        // the first 2 calls in this function work
        //so I am puzzled that this doesn't
    xmlhttp.open("GET",...);
    xmlhttp.send();}

var derivativeConstructor;
function server_query(){
    if(derivativeConstrucror===undefined){
        var derivativeConstructor=new Constructor(global_function);}
    derivativeConstructor.api_function();}

//old version works but clutters my code so I don't want it ->
//the actual code saves more lines of code
//and has better visibility
// so it's worth it
//unlike this example

function server_query(){xmlhttp=XMLHttpRequest();
    xmlhttp.onreadystatechange=function(){
        global_function(xmlhttp.responseText)}
    xmlhttp.open("GET",...);
    xmlhttp.send();} // this worked and all the rest should be practically unchanged

// where it all get's called from - should be unchanged between versions ->

<form action="" method="GET" onsubmit="(function(){return false;});">
    <input type="button" value="TEST" onclick="server_query();">
</form>

当我说我要改变的旧版本的作品时，我的意思是。我的问题是我第一次没有发布我的整个代码，所以人们给人的印象是我没有先尝试，然后不再看我实际问的内容。现在我也试图简化一些事情以消除我认为问题所在的地方的混乱，所以这不是实际的代码，可能无法在浏览器中粘贴复制 - 可能存在“小问题”。我只对我提出的问题感兴趣：我在哪里出错了函数可见性/闭包变量可见性/变量生命周期/无论我怎样修复它。

问题的旧版本：让我被烙印为没有通过回答/评论的2个人定义其功能的人 - ＆gt;

我有这个javascript代码应该简化服务器GET的创建：

function Generic_server_request(
        server_location,
        server_file,
        client_callback_function){
    this.server_location=server_location;
    this.server_file=server_file;
    this.query_parameters="";
    this.client_callback_function=client_callback_function;}
Generic_server_request.prototype
.server_request=function(){
    xmlhttp=new XMLHttpRequest();
    xmlhttp.onreadystatechange=function(){
        if(xmlhttp.readyState===4
            && xmlhttp.status===200)
                this.client_callback_function(
                    xmlhttp.responseText);
        else if((xmlhttp.status!==200) ||
                xmlhttp.status===200 &&
                xmlhttp.readyState!==2 &&
                xmlhttp.readyState!==3)
            alert("readystate "+xmlhttp.readyState
                +" status "+xmlhttp.status);}
    xmlhttp.open("GET",
        this.server_location+
        this.server_file+
        this.query_parameters,
        true);
    xmlhttp.send();}
Generic_server_request.prototype
.set_query_parameters=function(query_parameters){
    this.query_parameters=query_parameters}

function server_querry(input){
    if(query_request_manager === undefined){
        query_request_manager=new Generic_server_request(
            "http://localhost/cgi-bin/",
            "querry_handler.php",
            status_text);}
    query_request_manager.set_query_parameters("?input="+input);
    query_request_manager.server_request();}

问题是当服务器响应到来时，我在firebug控制台中得到了这个错误：“this.client_callback_function不是函数”。我可以使用一些帮助来了解范围发生了什么。

编辑我有一个以前的版本，它完成了使用Generic ...和server_querry（输入）在之前版本的server_querry（输入）中应该实现的一切，而status_text在代码atm的其他部分运行正常，所以不是问题。并且使用server_status和server_status的代码不会修改以前的预期功能。

此类内容也符合预期：

function Generic_server_request（...，client_callback_function）{ ... this.client_callback_function = client_callback_function; client_callback_function（ “测试”）; //作品 this.client_callback_function（ “测试”）; //工作原理

Answer 1

创建请求对象时，请使用：

new Generic_server_request(
 "http://localhost/cgi-bin/",
 "querry_handler.php",
 status_text
);

但在构造函数中，您的函数描述为：

function Generic_server_request(
 server_location,
 server_file,
 client_callback_function
)

因此，client_callback_function代替status_text传递{{1}}（不是函数）

Answer 2

虽然我创造了另一个问题，但我解决了我的初始问题，但如果我没有新的建议，这对另一个问题有好处。这是我目前相对于上面代码的通用外观的起点（顶部代码块）：

function global_function(server_response){}

function Constructor(global_function){
    this.local_reference_to_global_function=global_function;}
    //still doesn't work but now I intuitively get why it doesn't work
    //apparently this.xmlhttp is created new instead of being the one in api_function
    //and the 2 are not shared through the Constructor(global_function) environment

    //I could use some help from someone that would tell me
    //how to make minimal changes to get this.xmlhttp in this example
    //(this.xmlhttp in prototype.callback and prototype.api_function)
    //to reference the same object
    //or make equivalent minimal changes to other parts of the code

Constructor.prototype.callback=function(){
    this.xmlhttp.local_reference_to_global_function(this.xmlhttp.responseText);};
Constructor.prototype.api_function=function(){
    this.xmlhttp=new XMLHttpRequest();
    this.xmlhttp.onreadystatechange=this.callback();
    //xmlhttp.onreadystatechange=function(){
    //    this.local_reference_to_global_function(xmlhttp.responseText)} 
    // old version accesses local_reference_to_global_function
    // inside onreadystatechange function's new environment a new object
    // which is where I was stumped initially
    // new variable environment created that I didn't get
    xmlhttp.open("GET",...);
    xmlhttp.send();}

var derivativeConstructor;
function server_query(){
    if(derivativeConstrucror===undefined){
        var derivativeConstructor=new Constructor(global_function);}
    derivativeConstructor.api_function();}

Javascript GET回调函数未在服务器响应上定义

2 个答案: