)
) });
)
}, )
});
)
)
}, )
});
)
}, )
});
p.then(function (x) {
console.log(x)
}) //输出 1 链式调用1 链式调用2
// 4.v4.0 then函数中的onFullfilled和onRejected方法的返回值问题
function resolvePromise(promise, x, resolve, reject) {
if (promise === x) { throw new TypeError("type error") }
let isUsed;
if (x !== null && (typeof x === "object" || typeof x === "function")) {
try {
let then = x.then;
if (typeof then === "function") {
//是一个promise的情况
then.call(x, function (y) {
if (isUsed) return;
isUsed = true;
resolvePromise(promise, y, resolve, reject);
}, function (e) {
if (isUsed) return;
isUsed = true;
reject(e);
})
} else {
//仅仅是一个函数或者是对象
resolve(x)
}
} catch (e) {
if (isUsed) return;
isUsed = true;
reject(e);
}
} else {
//返回的基本类型，直接resolve
resolve(x)
}
}
myPromise.prototype.then = function (onFullfilled, onRejected) {
let self = this;
let promise2;
switch (self.status) {
case "pending":
promise2 = new myPromise(function (resolve, reject) {
self.onFullfilledArray.push(function () {
setTimeout(function () {
try {
let temple = onFullfilled(self.value);
resolvePromise(temple)
} catch (e) {
reject(e) //error catch
}
})
});
self.onRejectedArray.push(function () {
setTimeout(function () {
try {
let temple = onRejected(self.reason); resolvePromise(temple)
} catch (e) {
reject(e)// error catch
}
})
});
})
case "resolved":
promise2 = new myPromise(function (resolve, reject) {
setTimeout(function () {
try {
let temple = onFullfilled(self.value);
//将上次一then里面的方法传递进下一个Promise状态
resolvePromise(temple);
} catch (e) {
reject(e);//error catch
}
})
})
break;
case "rejected":
promise2 = new myPromise(function (resolve, reject) {
setTimeout(function () {
try {
let temple = onRejected(self.reason);
//将then里面的方法传递到下一个Promise的状态里
resolvePromise(temple);
} catch (e) {
reject(e);
}
})
})
break;
default:
}
return promise2;
}