Everyone knows that the full name of secondary encapsulation of jquery and Ajax is Asynchronous JavaScript and XML. The following article mainly introduces you to examples of secondary encapsulation of jquery ajax. The article introduces it through sample code. For details, friends who need it can take a look below. I hope it can help everyone.
The technologies involved in AJax:
1. Use CSS and XHTML to express.
2. Use DOM model for interaction and dynamic display.
3. Use XMLHttpRequest to communicate asynchronously with the server. (Core)
4. Use javascript to bind and call.
When our front-end processes data, it is inevitable to communicate with ajax and the background. Ajax communicates with the server through the XMLHttpRequest object. jquery encapsulates the $.ajax method based on XMLHttpReaquest for communication. The $.ajax method It is very practical and very simple to use. This second encapsulation of query ajax, refer to express to add middleware to process data, return Promise (Defferd) objects, reduce callbacks, and write ajax more concisely and elegantly.
$.ajax({ url: url, data: data, dataType: 'json', type: 'get', success: new Function(){}, error: new Function(){}, ....... })
Most of the time we only need to pass in the url and data to get the data we want.
Pain Points
But when using $.ajax in a project, it still has some pain points
It is the data returned by ajax for basically all projects now It has also been encapsulated twice and added information about the background processing business logic.
From returning data, it becomes {code: 200, data:{}, err_msg:''}
If every ajax request comes back, it must be judged whether the code is correct. The entire project is too redundant to process business logic or report errors.
$.ajax({ url: url, data: data, success: function(data){ if(data.code == 200) { dosomething() } else { alert(data.err_msg); } } })
In order to solve this problem, we use a function to encapsulate $.ajax again, and then process the business logic after judging whether it is correct or not. Or the error reminder can be extracted and made into a public part.
util.ajax = function(obj, successFn){ $.ajax({ url: obj.url || '/interface', data: obj.data || {}, dataType: obj.dataType || 'json', type: obj.type || 'get', success: function(data){ if (data.code != 200) { alert(data.err_msg); } else { successFn(data.data) } }, error: function(err){ alert(err) } }) }
promise
Use util.ajax instead of $.ajax to reduce business errors. Let's improve it again, instead of using callbacks, use promises to call, reducing callbacks and making the code clearer.
util.ajax = function(obj) { var deferred = $.Deferred(); $.ajax({ url: obj.url || '/interface', data: obj.data || {}, dataType: obj.dataType || 'json', type: obj.type || 'get', }).success(function (data) { if (data.code != 200) { deferred.reject(data.err_msg); } else { deferred.resolve(data.data) } }).error(function (err) { deferred.reject('接口出错,请重试'); }) return deferred.fail(function (err) { alert(err) }); } // 调用 var obj = { url: '/interface', data: { interface_name: 'name', interface_params: JSON.stringify({}) } }; util.ajax(obj) .done(function(data){ dosomething(data) })
Middleware
This is a public method, but sometimes we need to deal with differentiation. We refer to express to introduce a middleware to solve the differentiation problem.
util.ajax = function(obj, middleware) { var deferred = $.Deferred(); $.ajax({ url: obj.url || '/interface', data: obj.data || {}, dataType: obj.dataType || 'json', type: obj.type || 'get', }).success(function (data) { if (data.code != 200) { deferred.reject(data.err_msg); } else { deferred.resolve(data.data) } }).error(function (err) { deferred.reject('接口出错,请重试'); }) // 添加中间件 if(!middleware) { middleware = function(){}; } return deferred.done(middleware).fail(function (err) { message({ content: err, type: 'error', showLeftIcon: true, duration: 5000 }); }); } // 调用 // 调用 var obj = { url: '/interface', data: { interface_name: 'name', interface_params: JSON.stringify({}) } }; var middleware = function(data) { data.forEach(function(item){ item.fullName = item.firstName + item.lastName }) } util.ajax(obj, middleware) .done(function(data){ console.log(data.fullName) })
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实现方法:1、用“$("img").delay(毫秒数).fadeOut()”语句,delay()设置延迟秒数;2、用“setTimeout(function(){ $("img").hide(); },毫秒值);”语句,通过定时器来延迟。

修改方法:1、用css()设置新样式,语法“$(元素).css("min-height","新值")”;2、用attr(),通过设置style属性来添加新样式,语法“$(元素).attr("style","min-height:新值")”。

区别:1、axios是一个异步请求框架,用于封装底层的XMLHttpRequest,而jquery是一个JavaScript库,只是顺便封装了dom操作;2、axios是基于承诺对象的,可以用承诺对象中的方法,而jquery不基于承诺对象。

增加元素的方法:1、用append(),语法“$("body").append(新元素)”,可向body内部的末尾处增加元素;2、用prepend(),语法“$("body").prepend(新元素)”,可向body内部的开始处增加元素。

在jquery中,apply()方法用于改变this指向,使用另一个对象替换当前对象,是应用某一对象的一个方法,语法为“apply(thisobj,[argarray])”;参数argarray表示的是以数组的形式进行传递。

删除方法:1、用empty(),语法“$("div").empty();”,可删除所有子节点和内容;2、用children()和remove(),语法“$("div").children().remove();”,只删除子元素,不删除内容。

去掉方法:1、用“$(selector).removeAttr("readonly")”语句删除readonly属性;2、用“$(selector).attr("readonly",false)”将readonly属性的值设置为false。

on()方法有4个参数:1、第一个参数不可省略,规定要从被选元素添加的一个或多个事件或命名空间;2、第二个参数可省略,规定元素的事件处理程序;3、第三个参数可省略,规定传递到函数的额外数据;4、第四个参数可省略,规定当事件发生时运行的函数。


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