核心代码

为了精简代码，下面的Promise实现中去掉了代码校验，这样方便小伙伴看到Promise的核心逻辑。ES6语法。

活不多说，直接放代码

class PromiseTest {    executor = (resolve, reject) => {    }    constructor(executor) {        this.executor = executor;    }    then(sucess, error) {        let flag = true;        let resolveV;        let rejectV;        const resolve = (value) => {            flag = true;            resolveV =  sucess(value);        };        const reject = (value) => {            flag = false;            rejectV = error(value);        };        this.executor(resolve, reject);        // onfulfilled onrejected返回参数的传递  这是promise的精髓