1.resolve

2.reject

3.手写

1.resolve

//构造函数上添加 resolve 方法
Promise.resolve = function (value) {return new Promise((resolve, reject) => {if (value instanceof Promise) {value.then((val) => {resolve(val)},(err) => {reject(err)})} else {resolve(value)}})
}

2.reject

Promise.reject = function (value) {return new Promise((resolve, reject) => {reject(value)})
}