我知道这个对对象所有者的引用。但我很难尝试上课,同时试图确定这个所引用的内容。Javascript对象和这个关键字
想这是最好只显示代码:
function Ajax_Class(params) {
// Public Properties
this.Response = null;
// Private Properties
var RequestObj = null;
// Prototype Methods
this.OnReset = function() { };
this.OnOpenConn = function() { };
this.OnDataSent = function() { };
this.OnLoading = function() { };
this.OnSuccess = function() { alert("default onSuccess method."); };
this.OnFailure = function() { alert("default onFailure method."); };
// Public Methods
this.Close = function() { // Abort current Request
if (RequestObj) {
RequestObj.abort();
RequestObj = null;
return true;
} else return false;
};
// Private Methods
var Instance = function() { // To create instance of Http Request
try { return new XMLHttpRequest(); }
catch (error) {}
try { return new ActiveXObject("Msxml2.XMLHTTP"); }
catch (error) {}
try { return new ActiveXObject("Microsoft.XMLHTTP"); }
catch (error) {}
// throw new Error("Could not create HTTP request object.");
return false;
};
var ReadyStateHandler = function() {
// Switch through possible results
switch(RequestObj.readyState) {
case 0:
this.OnReset();
break;
case 1:
this.OnOpenConn();
break;
case 2:
this.OnDataSent();
break;
case 3:
this.OnLoading();
break;
case 4:
// Check Status
if (RequestObj.status == 200) {
// Handle Response
Response = HandleResponse();
// Call On Success
this.OnSuccess();
// Hide Loading Div
LoadingDiv(true);
} else {
this.OnFailure();
}
break;
} // End Switch
};
var Open = function() {
// In case it's XML, Override the Mime Type
if ((params["ResponseType"] == "XML") && (RequestObj.overrideMimeType))
RequestObj.overrideMimeType('text/xml');
//
if ((params["User"]) && (params["Password"]))
RequestObj.open(params["Method"], params["URL"], params["Async"], params["User"], params["Password"]);
else if (params["User"])
RequestObj.open(params["Method"], params["URL"], params["Async"], params["User"]);
else
RequestObj.open(params["Method"], params["URL"], params["Async"]);
// Set Request Header ?
if (params["method"] == "POST")
//this.SetRequestHeader("Content-Type", "application/x-www-form-urlencoded; charset=UTF-8");
RequestObj.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
};
var Send = function() {
if (params["Data"]) RequestObj.send(params["Data"]);
else RequestObj.send(null);
};
var HandleResponse = function() {
if (params["ResponseType"] == "JSON")
return ParseJSON(RequestObj.responseText);
else if (params["ResponseType"] == "XML")
return RequestObj.responseXML;
else
return RequestObj.responseText;
};
// Method ParseJSON
var ParseJSON = function(obj) {
if (obj)
return JSON.parse(obj);
}; // End ParseJSON
// Method LoadingDiv -> Either Shows or Hides the Loading Div
var LoadingDiv = function(hide) {
// Hide the Modal Window
if (hide) { document.getElementById("Async").style.display = "none"; return false; }
// Show Modal Window
document.getElementById("Async").style.display = "block";
// Reset the Position of the Modal_Content to 0, x and y
document.getElementById("Async_Container").style.left = "0px";
document.getElementById("Async_Container").style.top = "0px";
// Center the Modal Area, no matter what the content
var Screen_Width, Screen_Height;
// Get screen data
if (typeof(window.innerWidth) == "number") { Screen_Width = window.innerWidth; Screen_Height = window.innerHeight; } //Non-IE
else if (document.documentElement && (document.documentElement.clientWidth || document.documentElement.clientHeight)) { //IE 6+ in 'standards compliant mode'
Screen_Width = document.documentElement.clientWidth;
Screen_Height = document.documentElement.clientHeight;
} else if (document.body && (document.body.clientWidth || document.body.clientHeight)) { //IE 4 compatible
Screen_Width = document.body.clientWidth;
Screen_Height = document.body.clientHeight;
}
// Set Modal_Content Max Height to allow overflow
document.getElementById("Async_Container").style.maxHeight = Screen_Height - 200 + "px";
// Get Modal_Container data
var El_Width = document.getElementById("Async_Container").offsetWidth;
var El_Height = document.getElementById("Async_Container").offsetHeight;
// Set the Position of the Modal_Content
document.getElementById("Async_Container").style.left = ((Screen_Width/2) - (El_Width/2)) + "px";
document.getElementById("Async_Container").style.top = ((Screen_Height/2) - (El_Height/2)) + "px";
};
// Constructor
// Check the Params
// Required Params
if (!params["URL"]) return false;
// Default Params
params["Method"] = (!params["Method"]) ? "GET" : params["Method"]; // GET, POST, PUT, PROPFIND
params["Async"] = (params["Async"] === false) ? false : true;
params["ResponseType"] = (!params["ResponseType"]) ? "JSON" : params["ResponseType"]; // JSON, TXT, XML
params["Loading"] = (params["Loading"] === false) ? false : true;
// Optional Params
// params["User"])
// params["Password"]
// Create Instance of Http Request Object
RequestObj = Instance();
// Handle Ajax according to Async
if (params["Async"]) {
// Handle what should be done in case readyState changes
if (params["Loading"]) LoadingDiv();
// State Handler || Response is Handled within the code
RequestObj.onreadystatechange = ReadyStateHandler;
// Open & Send
Open();
Send();
} else {
// Handle the Loading Div
if (params["Loading"]) LoadingDiv();
// Open & Send
Open();
Send();
// Handle Response
this.Response = HandleResponse();
// No State Handler, Application has been waiting for modifications.
//this.OnSuccess(Response);
// Handle the Loading Div
LoadingDiv(true);
}
// no problems?
return true;
} // End Ajax
然后,在页面内:
window.onload = function() {
update_states = function() {
this.OnSuccess = function() {
alert("overriden onSuccess Method");
};
};
update_states.prototype = new Ajax_Class({URL:"ajax/states.php?id=5&seed="+Math.random()});
run_update_states = new update_states;
} // Window Onload
我试图做的是有一个默认的onSuccess(等)方法,并且在需要的情况下,我可以使用子类方法覆盖默认方法,但在HttpRequest状态更改时它仍会自动调用。
我很感激,如果有人能指出我在正确的方向,并会惊讶,如果我能明白为什么这不在这个circunstance工作,以及如何使其参考正确的对象。
感谢您的任何帮助。
Firefox或Chrome中的'console.log(this)'有助于确定代码(范围)中某些部分所指的是什么。另外,'this'不是对象所有者,它是对象本身。另一个方便的提示是使用'typeof(this)'或'this.constructor'来获取对象的更多信息。 – MalSu
我明白了。它的方式是this.OnSuccess,如果指向对象xmlHttpRequest。基于你所说的话是有道理的。但是,当我尝试,而在类块,如下所示:var self = this;那么我无法重写类方法,因为它总是指的是主类。这有任何意义吗? –
呵呵,不是太多... – MalSu