$.ajax

基于$.ajax声明一个简单的AjaxHelper构造器，AjaxHelper构造器的原型对象包含5个方法，分别用于处理GET, POST, PUT, DELETE和JSONP请求。

function AjaxHelper() {
    this.ajax = function(url, type, dataType, data, callback) {
        $.ajax({
            url: url,
            type: type,
            dataType: dataType,
            data: data,
            success: callback,
            error: function(xhr, errorType, error) {
                alert('Ajax request error, errorType: ' + errorType +  ', error: ' + error)
            }
        })
    }
}
AjaxHelper.prototype.get = function(url, data, callback) {
    this.ajax(url, 'GET', 'json', data, callback)
}
AjaxHelper.prototype.post = function(url, data, callback) {
    this.ajax(url, 'POST', 'json', data, callback)
}

AjaxHelper.prototype.put = function(url, data, callback) {
    this.ajax(url, 'PUT', 'json', data, callback)
}

AjaxHelper.prototype.delete = function(url, data, callback) {
    this.ajax(url, 'DELETE', 'json', data, callback)
}

AjaxHelper.prototype.jsonp = function(url, data, callback) {
    this.ajax(url, 'GET', 'jsonp', data, callback)
}

AjaxHelper.prototype.constructor = AjaxHelper

发送get请求。实例：（vue实例）

var ajaxHelper = new AjaxHelper()

var demo = new Vue({
    el: '#app',
    data: {
        gridColumns: ['customerId', 'companyName', 'contactName', 'phone'],
        gridData: [],
        apiUrl: 'http://localhost:15341/api/Customers'
    },
    ready: function() {
        this.getCustomers()
    },
    methods: {

        getCustomers: function() {
            // 定义vm变量，让它指向this,this是当前的Vue实例
            var vm = this,
                callback = function(data) {
                    // 由于函数的作用域，这里不能用this
                    vm.$set('gridData', data)
                }
            ajaxHelper.get(vm.apiUrl, null, callback)
        }
    }
})

 --纯原生js代码片段：

var ajax = function() {};
 ajax.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);
         };
         if (method !== "POST") {
             url += "?" + JSONStringify(postVars);
             postVars = null;
         }
         xhr.open(method, url, true);
         xhr.send(postVars);
     },
     createXhrObject: function() {
         var methods = [
             function() { return new XMLHttpRequest(); },
             function() { return new ActiveXObject("Msxml2.XMLHTTP"); },
             function() { return new ActiveXObject("Microsoft.XMLHTTP"); }
         ],
         i = 0,
         len = methods.length;
         for (; i < len; i++) {
             try {
                 methods[i];
             } catch(e) {
                 continue;
             }
             this.createXhrObject = methods[i];
             return methods[i];
         }
         throw new Error("ajax created failure");
     },
     JSONStringify: function(obj) {
         return JSON.stringify(obj).replace(/"|{|}/g, "")
                     .replace(/b:b/g, "=")
                     .replace(/b,b/g, "&");
     }
 };