目录#介绍Promise#Promise.prototype.then(onFulfilled,onRejected)#Promise.prototype.catch(onRejected)#Promise.prototype.finally(onRejected) #Promise.resolve() #Promise.reject() #Promise.all([]) #Promise.race([])#封装原生简易Ajax请求#介绍Promise首先说下 Promise也是个 构造函数通过new关键字来实例化一个promise对象 用来将一些异步操作给实现队列化也就