;(function($) {
// override：新的請求是否要覆蓋之前的請求
function AjaxQueue(override) {
this.override = !!override;
};
AjaxQueue.prototype = {
requests: new Array(),
offer: function(options) {
var _self = this;
var xhrOptions = $.extend({}, options, {
complete: function(jqXHR, textStatus) {
// 支持complete是函數(shù)數(shù)組的情況
if($.isArray(options.complete)) {
var funcs = options.complete;
for(var i = 0, len = funcs.length; i < len; i++)
funcs[i].call(this, jqXHR, textStatus);
} else {
if(options.complete)
options.complete.call(this, jqXHR, textStatus);
}
// 處理結(jié)束，從隊(duì)列中發(fā)出下一個(gè)ajax請求
_self.poll();
},
beforeSend: function(jqXHR, settings) {
if(options.beforeSend)
var ret = options.beforeSend.call(this, jqXHR, settings);
// 如果當(dāng)前ajax請求因?yàn)槟承┰虮怀蜂N了，那么去發(fā)下一個(gè)ajax請求
if(ret === false) {
_self.poll();
return ret;
}
}
});
// 如果支持覆蓋，那么調(diào)用replace
if(this.override) {
// console.log('go override');
this.replace(xhrOptions);
// 反之放入隊(duì)列
} else {
// console.log('go queue');
this.requests.push(xhrOptions);
if(this.requests.length == 1) {
$.ajax(xhrOptions);
}
}
},
// 撤銷前一個(gè)請求，發(fā)送新的請求
replace: function(xhrOptions) {
var prevRet = this.peek();
if(prevRet != null) {
// jquery源碼中可以看到此方法
prevRet.abort();
}
this.requests.shift();
this.requests.push($.ajax(xhrOptions));
},
// 輪詢隊(duì)列 發(fā)送下一個(gè)請求
poll: function() {
if(this.isEmpty()) {
return null;
}
var processedRequest = this.requests.shift();
var nextRequest = this.peek();
if(nextRequest != null) {
$.ajax(nextRequest);
}
return processedRequest;
},
// 返回隊(duì)列頭部的請求
peek: function() {
if(this.isEmpty()) {
return null;
}
var nextRequest = this.requests[0];
return nextRequest;
},
// 判斷隊(duì)列是否為空
isEmpty: function() {
return this.requests.length == 0;
}
};
var queue = {};
// 管理AjaxQueue的簡單對象
var AjaxManager = {
// 創(chuàng)建新的ajaxQueue
createQueue: function(name, override) {
return queue[name] = new AjaxQueue(override);
},
// 清除對應(yīng)name的ajaxQueue
destroyQueue: function(name) {
if(queue[name]) {
queue[name] = null;
delete queue[name];
}
},
// 根據(jù)name得到對應(yīng)的ajaxQueue
getQueue: function(name) {
return ( queue[name] ? queue[name] : null);
}
};
// 跟jQuery關(guān)聯(lián)起來，給個(gè)簡稱，方便調(diào)用
$.AM = AjaxManager;
})(jQuery);