简要:ajax请求具有能够触发各类事件的功能,包括:触发全局事件,请求发送前事件,请求开始事件,请求结束事件等等,贯穿整个ajax请求过程,这是非常有用的,我们可以利用这些事件来做一些非常有意思的事情比如:拦截器,权限管理等等,另外$.ajax()貌似会返回一个异步请求对象xhr,这个xhr也是继承了defer的promise对象。这些事件中全局事件是绑定在document上的,局部事件由settings.content指定。(不管怎么说事件都是绑定在dom元素上的,至于事件为什么要与dom关联,可能是为了重用event.js吧,本人在此挖个坑,若有人知道,希望能指点一二)。
闲话少说,直接上代码:
/** * * 触发自定义事件 * @param context * @param eventName * @param data * @returns {boolean} */ function triggerAndReturn(context, eventName, data) { var event = $.Event(eventName) //创建Event对象 $(context).trigger(event, data) //触发,这里event参数也可以为字符串,但这里对eventName的校验放到$.Event里面区实现 return !event.isDefaultPrevented() //TODO:返回event.isDefaultPrevented? } // trigger an Ajax "global" event /** * 触发ajax的全局事件 * @param settings * @param context * @param eventName * @param data * @returns {*} */ function triggerGlobal(settings, context, eventName, data) { //settings.global 是否触发ajax的全局事件 if (settings.global) return triggerAndReturn(context || document, eventName, data); }
triggerGlobal是一个公用函数,在ajaxStart,ajaxStop,ajaxBeforeSend,,ajaxSend,ajaxSuccess,ajaxError,ajaxComplete这些方法中触发全局事件,
除了ajaxStart,和ajaxStop 触发绑定在document上的对应事件外,其他的会触发settings.content绑定的事件。
如果你在settings里不设置global为true,则ajax是不会触发各类事件的。
$.active = 0 /** * 触发全局 ‘ajaxStart’事件 * @param settings */ function ajaxStart(settings) { //settings.global 传递进来的是否触发全局事件参数 //$.active++ === 0 $.active = 0,此判断才会true if (settings.global && $.active++ === 0) triggerGlobal(settings, null, 'ajaxStart') } /** * 尝试抛出所有请求停止事件,写法和ajaxStart相同 * @param settings */ function ajaxStop(settings) { if (settings.global && !(--$.active)) triggerGlobal(settings, null, 'ajaxStop') }
ajaxStart:如果允许触发全局事件(settings.global),且当前事件为$内部第一个ajax请求,则执行document所绑定的ajaxStart事件。
$.active++ === 0会先若$.active与0比较,然后自加。
// triggers an extra global event "ajaxBeforeSend" that's like "ajaxSend" but cancelable //触发全局ajaxBeforeSend事件,如果返回false,则取消此次请求 /** * 请求前置器, beforeSend ,返回false,取消此次请求 * 或抛出 ajaxBeforeSend 全局事件 * 抛出ajaxSend事件 * * @param xhr * @param settings * @returns {boolean} */ function ajaxBeforeSend(xhr, settings) { var context = settings.context if (settings.beforeSend.call(context, xhr, settings) === false || triggerGlobal(settings, context, 'ajaxBeforeSend', [xhr, settings]) === false) return false triggerGlobal(settings, context, 'ajaxSend', [xhr, settings]) }
ajaxBeforeSend: 可用于拦截请求,判断并决定请求是否发送。这里定义了2个位置可以处理请求,1:settings.beforeSend 函数,2:settings.context所绑定的
ajaxBeforeSend事件。只要其中有一个function返回false,则终止请求。
/** * 请求成功调用函数 * @param data * @param xhr * @param settings * @param deferred */ function ajaxSuccess(data, xhr, settings, deferred) { var context = settings.context, status = 'success' //调用success函数 settings.success.call(context, data, status, xhr) //调用所有成功回调函数 if (deferred) deferred.resolveWith(context, [data, status, xhr]) //抛出全局事件 'ajaxSuccess' triggerGlobal(settings, context, 'ajaxSuccess', [xhr, settings, data]) //请求完成 ajaxComplete(status, xhr, settings) } // type: "timeout", "error", "abort", "parsererror" /** * 请求失败调用函数 * @param error * @param type * @param xhr * @param settings * @param deferred */ function ajaxError(error, type, xhr, settings, deferred) { var context = settings.context settings.error.call(context, xhr, type, error) if (deferred) deferred.rejectWith(context, [xhr, type, error]) triggerGlobal(settings, context, 'ajaxError', [xhr, settings, error || type]) ajaxComplete(type, xhr, settings); } // status: "success", "notmodified", "error", "timeout", "abort", "parsererror" /** * 请求完成调用函数 * @param status * @param xhr * @param settings */ function ajaxComplete(status, xhr, settings) { var context = settings.context //执行complete settings.complete.call(context, xhr, status) triggerGlobal(settings, context, 'ajaxComplete', [xhr, settings]) //尝试抛出所有请求停止事件 ajaxStop(settings) }
$.ajax({url:'http://192.168.1.189:8080/api/v1/_products/get',data:{name:'zhutao'},method:'POST'})
.then(function(){console.log(arguments);}); Object {} [Object, "success", Object]
$.ajax({url:'http://192.168.1.189:8080/api/v1/_products/get',data:{name:'zhutao'},method:'POST'})
.then(function(){console.log('SUCCESS',arguments);}); Object {} SUCCESS [Object, "success", Object]0: Objectcode: 9998entity: nullmessage: "商品不存在"__proto__: Object__defineGetter__: __defineGetter__()__defineSetter__: __defineSetter__()__lookupGetter__: __lookupGetter__()__lookupSetter__: __lookupSetter__()constructor: Object()hasOwnProperty: hasOwnProperty()isPrototypeOf: isPrototypeOf()propertyIsEnumerable: propertyIsEnumerable()toLocaleString: toLocaleString()toString: toString()valueOf: valueOf()get __proto__: get __proto__()set __proto__: set __proto__()1: "success"2: Objectabort: (e)always: ()complete: ()done: ()error: ()fail: ()getAllResponseHeaders: ()getResponseHeader: (e)overrideMimeType: (e)pipe: ()progress: ()arguments: nullcaller: nulllength: 0name: ""prototype: Object__proto__: ()<function scope>promise: (e)arguments: nullcaller: nulllength: 1name: ""prototype: Object__proto__: ()<function scope>readyState: 4responseJSON: ObjectresponseText: "{"code":9998,"message":"商品不存在","entity":null}"setRequestHeader: (e,t)arguments: nullcaller: nulllength: 2name: ""prototype: Object__proto__: ()<function scope>state: ()status: 200statusCode: (e)statusText: "OK"success: ()then: ()__proto__: Objectcallee: ()arguments: nullcaller: nulllength: 0name: ""prototype: Object__proto__: ()<function scope>length: 3Symbol(Symbol.iterator): values()__proto__: Object
$.ajax({url:'/get',data:{name:'zhutao'}}).then(function(){console.log('SUCCESS',arguments);},function(){console.log('error');}); Object {} GET http://192.168.1.198:8000/get?name=zhutao 404 (Not Found) error
执行ajax的回调函数有两种,1:$.ajax({.....,success:function(){}}); 2:$.ajax({...}).then(function(){});
settings.success 会先执行,然后执行deffer.resolve();利用$.ajax()返回的promise,我们能很方便的做很多事情。