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test.js
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58 lines (58 loc) · 1.84 KB
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class Promise {
constructor(executor){
this.PromiseState = 'pendding'
this.PromiseResult = null
this.callbacks = []
const self = this
function resolve(data){
if(self.PromiseState !== 'pendding') return
self.PromiseState = 'fulfilled'
self.PromiseResult = data
if(self.callbacks.length > 0){
self.callbacks.forEach(callback => {
callback.onResolve(data)
})
}
}
function reject(err){
if(self.PromiseState !== 'pendding') return
self.PromiseState = 'rejected'
self.PromiseResult = err
if(self.callbacks.length > 0){
self.callbacks.forEach(callback => {
callback.onResolve(data)
})
}
}
try {
executor(resolve,reject)
} catch (error) {
reject(error)
}
}
then(onResolve, onReject){
return new Promise((resolve, reject) => {
try {
if(this.PromiseState === 'fulfilled'){
let res = onResolve(this.PromiseResult)
if(res instanceof Promise) {
return res.then(val => {
resolve(val)
}, err => {
reject(err)
})
}else {
resolve(res)
}
}
} catch (error) {
reject(error)
}
if(this.PromiseState === 'rejected') onReject(this.PromiseResult)
if(this.PromiseState === 'pendding') {
// 保存回调函数
this.callbacks.push({onResolve,onReject})
}
})
}
}