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Copy path4 - Building an XHR connection queue.js
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Copy path4 - Building an XHR connection queue.js
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227 lines (214 loc) · 5.1 KB
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// XMLHttpRequest的核心工具类
var asyncRequest = (function() {
function handleReadyState(o, callback) {
var poll = window.setInterval(
function() {
if (o && o.readyState == 4) {
window.clearInterval(poll);
if (callback) {
callback(o);
}
}
},
50
);
}
var getXHR = function() {
var http;
try {
http = new XMLHttpRequest;
getXHR = function() {
return new XMLHttpRequest;
};
}
catch(e) {
var msxml = [
'MSXML2.XMLHTTP.3.0',
'MSXML2.XMLHTTP',
'Microsoft.XMLHTTP'
];
for (var I = 0, len = msxml.length; i < len; ++i) {
try {
http = new ActiveXObject(msxml[i]);
getXHR = function() {
return new ActiveXObject(msxml[i]);
};
break;
}
catch(e) {}
}
}
return http;
};
return function(method, uri, callback, postData) {
var http = getXHR();
http.open(method, uri, true);
handleReadyState(http, callback);
http.send(postData || null);
return http;
};
})();
// 有了这个方法，就可以用类似于讲述链式调用的第六章中的风格进行开发
Function.prototype.method = function(name, fn) {
this.prototype[name] = fn;
return this;
};
// From the Mozilla Developer Center website at http://developer.mozilla.org/en/docs/New_in_JavaScript_1.6#Array_extras.
if ( !Array.prototype.forEach ) {
Array.method('forEach', function(fn, thisObj) {
var scope = thisObj || window;
for ( var i = 0, len = this.length; i < len; ++i ) {
fn.call(scope, this[i], i, this);
}
});
}
if ( !Array.prototype.filter ) {
Array.method('filter', function(fn, thisObj) {
var scope = thisObj || window;
var a = [];
for ( var i = 0, len = this.length; i < len; ++i ) {
if ( !fn.call(scope, this[i], i, this) ) {
continue;
}
a.push(this[i]);
}
return a;
});
}
// 添加观察者系统
window.DED = window.DED || {};
DED.util = DED.util || {};
DED.util.Observer = function() {
this.fns = [];
}
DED.util.Observer.prototype = {
subscribe: function(fn) {
this.fns.push(fn);
},
unsubscribe: function(fn) {
this.fns = this.fns.filter(
function(el) {
if ( el !== fn ) {
return el;
}
}
);
},
fire: function(o) {
this.fns.forEach(
function(el) {
el(o);
}
);
}
};
// 开发队列的基本框架
DED.Queue = function() {
// Queued requests. 数组字面量，用于保存对每一个请求的引用
this.queue = [];
// Observable Objects that can notify the client of interesting moments
// on each DED.Queue instance.
this.onComplete = new DED.util.Observer;
this.onFailure = new DED.util.Observer;
this.onFlush = new DED.util.Observer;
// Core properties that set up a frontend queueing system.
this.retryCount = 3;
this.currentRetry = 0;
this.paused = false;
this.timeout = 5000;
this.conn = {};
this.timer = {};
};
// 为框架提供需要的方法
DED.Queue.
method('flush', function() {
if (!this.queue.length > 0) {
return;
}
if (this.paused) {
this.paused = false;
return;
}
var that = this;
this.currentRetry++;
var abort = function() {
that.conn.abort();
if (that.currentRetry == that.retryCount) {
that.onFailure.fire();
that.currentRetry = 0;
} else {
that.flush();
}
};
this.timer = window.setTimeout(abort, this.timeout);
var callback = function(o) {
window.clearTimeout(that.timer);
that.currentRetry = 0;
that.queue.shift();
that.onFlush.fire(o.responseText);
if (that.queue.length == 0) {
that.onComplete.fire();
return;
}
// recursive call to flush
that.flush();
};
this.conn = asyncRequest(
this.queue[0]['method'],
this.queue[0]['uri'],
callback,
this.queue[0]['params']
);
}).
method('setRetryCount', function(count) {
this.retryCount = count;
}).
method('setTimeout', function(time) {
this.timeout = time;
}).
method('add', function(o) {
this.queue.push(o);
}).
method('pause', function() {
this.paused = true;
}).
method('dequeue', function() {
this.queue.pop();
}).
method('clear', function() {
this.queue = [];
});
/* Usage. */
var q = new DED.Queue;
// Reset our retry count to be higher for slow connections.
q.setRetryCount(5);
// Decrease timeout limit because we still want fast connections to benefit.
q.setTimeout(1000);
// Add two slots.
q.add({
method: 'GET',
uri: '/path/to/file.php?ajax=true'
});
q.add({
method: 'GET',
uri: '/path/to/file.php?ajax=true&woe=me'
});
// Flush the queue.
q.flush();
// Pause the queue, retaining the requests.
q.pause();
// Clear our queue and start fresh.
q.clear();
// Add two requests.
q.add({
method: 'GET',
uri: '/path/to/file.php?ajax=true'
});
q.add({
method: 'GET',
uri: '/path/to/file.php?ajax=true&woe=me'
});
// Remove the last request from the queue.
q.dequeue();
// Flush the queue again.
q.flush();