Противоположное шаблону Promise
По словам одного из пользователей сайта, он использует аналогичные методы, как Promise.
class Task {
static PENDING = 'pending'
static FULFILLED = 'fulFilled'
static REJECTED = 'rejected'
static WaitResults = []
constructor(executor) {
this.status = Task.PENDING
this.value = undefined
this.reason = undefined
this.onResolvedCallbacks = []
this.onRejectedCallbacks = []
// 成功
let _resolve = (value) => {
// 如果是异步的请求的结果，将wait在Task.wait中统一处理
if (this.status == Task.PENDING) {
if (value && value.wait instanceof Function) {
Task.WaitResults.push({
handle: value.wait,
resolve: _resolve,
reject: _reject
})
} else {
this.status = Task.FULFILLED
this.value = value
let handler;
while (handler = this.onResolvedCallbacks.shift()) {
handler(this.reason)
}
}
}
}
//失败
let _reject = (reason) => {
if (this.status == Task.PENDING) {
this.status = Task.REJECTED
this.reason = reason
let handler;
while (handler = this.onRejectedCallbacks.shift()) {
handler(this.value)
}
}
}
executor(_resolve, _reject)
}
then(onFulfilled, onRejected) {
let promise = this
return new Task((resolve, reject) => {
function handler(value) {
var ret = typeof onFulfilled === 'function' && onFulfilled(value);
if (ret instanceof Task) {
ret.then(resolve, reject)
} else {
resolve(ret);
}
}
function errback(reason) {
let ret = typeof onRejected === 'function' && onRejected(reason) || reason;
if (ret instanceof Task) {
ret.then(resolve, reject)
} else {
reject(ret);
}
}
if (promise.status === Task.PENDING) {
//Log("PENDING")
promise.onResolvedCallbacks.push(handler);
promise.onRejectedCallbacks.push(errback);
} else if (promise.status === Task.FULFILLED) {
//Log("FULFILLED")
handler(promise.value);
} else if (promise.status === Task.REJECTED) {
//Log("REJECTED")
errback(promise.reason);
}
})
}
catch(onReJected) {
return this.then(undefined, onReJected)
}
//同步多个异步操作
static all = (list) => {
return new Task((resolve, reject) => {
var resArray = []
let index = 0
function processData(i, data) {
resArray[i] = data
index += 1
if (index == list.length) {
resolve(resArray)
}
}
for (let i = 0; i < list.length; i++) {
let item = list[i]
if (item instanceof Task) {
item.then(data => {
processData(i, data);
}, err => {
reject(err)
return;
})
} else {
processData(i, item);
}
}
})
}
//获取异步结果
static wait = function () {
let obj;
while (obj = Task.WaitResults.shift()) {
if (!obj) break;
let { handle, resolve, reject } = obj;
let data = handle(6000)
if (data !== undefined) {
resolve(data)
} else {
// 如果异步超时返回wait对象，可以后续再尝试，或者直接查询请求结果。
reject(handle)
}
}
}
}
function main() {
exchange.SetContractType("swap")
new Task(function (resolve, reject) {
resolve(exchange.Go("GetDepth"))
}).then(data => {
Log(data)
return data
}).then((data) => {
//链式执行
Log(data)
})
new Task(function (resolve, reject) {
reject("错误测试")
}).then(data => {
Log(data)
}, error => {
Log(error)
return "将错误处理后传递到catch方法"
}).catch(error => {
Log(error)
})
Task.all([
new Task(function (resolve, reject) {
resolve(exchange.Go("GetDepth"))
}),
new Task(function (resolve, reject) {
resolve(exchange.Go("GetTicker"))
}),
new Task(function (resolve, reject) {
resolve(100)
}),
{ a: 1 },
{ b: 2 }
]).then(data => {
Log(data[0])
Log(data[1])
Log(data[2])
Log(data[3])
Log(data[4])
})
//同步多个请求出现异常，需要处理查询异步请求的结果
Task.all([
new Task((resolve, reject) => {
resolve(1)
}),
new Task((resolve, reject) => {
resolve(2)
}),
new Task((resolve, reject) => {
//出错
reject(3)
}),
new Task((resolve, reject) => {
resolve(4)
}),
]).then((data) => {
console.log(data)
}, error => {
console.log("error", error)
return 5
}).catch(error => {
console.log("catch", error)
})
//必须执行，这里将会调用所有异步的wait方法，获取结果。
Task.wait()
}