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Copy path3 - XHR factory example.js
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Copy path3 - XHR factory example.js
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52 lines (45 loc) · 1.7 KB
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/* AjaxHandler interface. */
var AjaxHandler = new Interface('AjaxHandler', ['request', 'createXhrObject']);
/* SimpleHandler class. */
var SimpleHandler = function() {}; // implements AjaxHandler
SimpleHandler.prototype = {
request: function(method, url, callback, postVars) {
var xhr = this.createXhrObject();
xhr.onreadystatechange = function() {
if(xhr.readyState !== 4) return;
(xhr.status === 200) ?
callback.success(xhr.responseText, xhr.responseXML) :
callback.failure(xhr.status);
};
xhr.open(method, url, true);
if(method !== 'POST') postVars = null;
xhr.send(postVars);
},
createXhrObject: function() { // Factory method.
var methods = [
function() { return new XMLHttpRequest(); },
function() { return new ActiveXObject('Msxml2.XMLHTTP'); },
function() { return new ActiveXObject('Microsoft.XMLHTTP'); }
];
for(var i = 0, len = methods.length; i < len; i++) {
try {
methods[i]();
}
catch(e) {
continue;
}
// If we reach this point, method[i] worked.
this.createXhrObject = methods[i]; // Memoize the method. 记住该方法
return methods[i](); // 原书中的代码少了一对括号，这里需要多加一对括号才可以正确返回XMLHttpRequeset
}
// If we reach this point, none of the methods worked.
throw new Error('SimpleHandler: Could not create an XHR object.');
}
};
/* Usage. */
var myHandler = new SimpleHandler();
var callback = {
success: function(responseText) { alert('Success: ' + responseText); },
failure: function(statusCode) { alert('Failure: ' + statusCode); }
};
myHandler.request('GET', 'script.php', callback);