js手写'Promise'

/* * pending:初始化成功 * fulfilled:成功 * rejected：失败 * */function Promise(executor) {// 执行器 ???this.status = ‘pending‘; ???this.value = undefined; ???this.reason = undefined; ???this.fulfilledCallback = []; ???this.rejectCallback = []; ???let resolve = (value)=>{ ???????if(this.status==‘pending‘){ ???????????this.status = ‘resolve‘; ???????????this.value = value; ???????????this.fulfilledCallback.forEach(fn=>fn()) ???????} ???}; ???let reject = (reason)=>{ ???????if(this.status ==‘pending‘){ ???????????this.status = ‘reject‘; ???????????this.reason = reason; ???????????this.rejectCallback.forEach(fn=>fn()) ???????} ???}; ???try{ ???????executor(resolve,reject) ???}catch(e){ ???????reject(e) ???}}Promise.prototype.then = function (onfulfilled,onrejected) { ???if(this.status == ‘resolve‘){ ???????onfulfilled(this.value) ???} ???if(this.status == ‘reject‘){ ???????onrejected(this.reason) ???} ???if(this.status == ‘pending‘){ ???????this.fulfilledCallback.push(()=>{ ???????????onfulfilled(this.value) ???????}); ???????this.rejectCallback.push(()=>{ ???????????onrejected(this.reason) ???????}) ???}};var a = new Promise((resolve,reject)=>{ ???setTimeout(()=>{ ???????resolve(10) ???})});a.then((res)=>{ ???console.log(res);});