function resolvePromise(promise2,x,resole,reject) {
if (promise2 === x) {
try {
//return reject(new Error("循环引用"));
}catch (e) {
return reject("循环引用");
}
}
if (typeof x === "function" || (typeof x === "object" && x !== null)) {
var called;
try {
let then = x.then;
if (typeof then === "function") {
then.call(function (x,y) {
if (called) return;
called = true;
resolvePromise(promise2, y, resole, reject);
},function (r) {
if (called) return;
called = true;
reject(r);
})
}else {
resole(x);
}
}catch (e) {
if (called) return;
called = true;
reject(e);
}
}else {
resole(x);
}
}
function Promise(executor) {
this.value = "";
this.reason = "";
this.status = "pending";
this.resolveCallbacks = [];
this.rejectedCallbacks = [];
try {
executor(this.resolve.bind(this),this.reject.bind(this))
}catch (e) {
this.reject.call(this,e);
}
}
Promise.prototype.resolve = function (value) {
if (this.status === "pending") {
this.status = "fulfilled";
this.value = value;
for (var i = 0; i < this.resolveCallbacks.length; i++) {
this.resolveCallbacks[i]();
}
}
};
Promise.prototype.reject = function (reason) {
if (this.status === 'pending') {
this.status = "rejected";
this.reason = reason;
for (var i = 0; i < this.rejectedCallbacks.length; i++) {
this.rejectedCallbacks[i]();
}
}
};
Promise.prototype.then = function (onfulfilled,onrejected) {
var promise2,_this=this;
promise2 = new Promise(function (resolve, reject) {
if (_this.status === "fulfilled") {
setTimeout(function () {
try {
var x = onfulfilled(_this.value);
resolvePromise(promise2, x, resolve, reject);
} catch (e) {
reject(e);
}
}, 0);
}
if (_this.status === "rejected") {
setTimeout(function () {
try {
let x = onrejected(_this.reason);
resolvePromise(promise2, x, resolve, reject);
} catch (e) {
reject(e);
}
}, 0);
}
if (_this.status === "pending") {
_this.resolveCallbacks.push(function () {
setTimeout(function () {
try {
let x = onfulfilled(_this.value);
resolvePromise(promise2, x, resolve, reject);
} catch (e) {
reject(e);
}
},0)
});
_this.rejectedCallbacks.push(function () {
setTimeout(function () {
try {
let x = onrejected(_this.reason);
resolvePromise(promise2, x, resolve, reject);
} catch (e) {
reject(e);
}
}, 0);
})
}
});
return promise2;
};
Promise.prototype.catch = function (rejectFuc) {
return this.then(null, rejectFuc);
};
Promise.prototype.finally = function (callback) {
this.then(callback, callback);
};
Promise.resolve = function (value) {
return new Promise(function (resolve, reject) {
resolve(value);
});
};
Promise.reject = function (reason) {
return new Promise(function (resolve,reject) {
reject(reason);
})
};
Promise.race = function (values) {
return new Promise(function (resolve,reject) {
for (var i=0;i<values.length;i++){
var current = values[i];
if (typeof current === "function" || (typeof current === "object") && current !== null) {
var then = current.then;
if (typeof then === "function") {
then.call(current, resolve, reject);
}else {
reject(current);
}
}else {
resolve(current);
}
}
})
};
var P = new Promise(function (resolve,reject) {
resolve(11);
});
P.then(function (data) {
});
手写es5版的promise
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转载自blog.csdn.net/qq_28473733/article/details/105457443
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