`resolvePromise(promise2, x, resolve, reject) { let called = false; // 避免多次调用 if (promise2 === x) { return reject(new TypeError('循环引用')); } else if (x != null && ((typeof x === 'object') || (typeof x === 'function'))) { try { // 是否是thenable对象（具有then方法的对象/函数） let then = x.then; if (typeof then === 'function') { then.call(x, y => { if (called) return; called = true; resolvePromise(promise2, y, resolve, reject); }, r => { if (called) return; called = true; reject(r); }) } else { // 说明是一个普通对象/函数 resolve(x); } } catch (e) { if (called) return; called = true; reject(e); } } else { resolve(x); } } then(onFulfilled, onReject) { onFulfilled = typeof onFulfilled === "function" ? onFulfilled : value => value; onRejected = typeof onRejected === "function" ? onRejected : reason => { throw reason; }; let promise2 = new Promise((resolve, reject) => { if (this.PromiseState === FULFFILLED) { try { setTimeout(() => { let x = onFulfilled(this.PromiseResult) resolvePromise(promise2, x, resolve, reject) }, 0); } catch (e) { reject(e) } } else if (this.PromiseState === REJECTED) { try { setTimeout(() => { let x = onFulfilled(this.PromiseResult) resolvePromise(promise2, x, resolve, reject) }, 0); } catch (e) { reject(e) } } else if (this.PromiseState === PENDING) { this.onFulfilledCallbacks.push((value) => { try { let x = onFulfilled(value) resolvePromise(promise2, x, resolve, reject) } catch (e) { reject(e) } }) this.onRejectedCallbacks.push((value) => { try { let x = onReject(value) resolvePromise(promise2, x, resolve, reject) } catch (e) { reject(e) } }) }
})
return promise2
}`
