class Commitment {
static PENDING = "待定"
static FULFILLED = "成功"
static REJECTED = "拒绝"
constructor(func) {
this.status = Commitment.PENDING
this.result = null
this.resolveCallbacks = []
this.rejectCallbacks = []
try {
func(this.resolve.bind(this), this.reject.bind(this))
}
catch (error) {
this.reject(error)
}
}
resolve(result){
setTimeout(() => {
if(this.status === Commitment.FULFILLED) {
this.status = Commitment.FULFILLED
this.result = result
this.resolveCallbacks.forEach(callback => {
callback(result)
})
}
})
}
reject(){
setTimeout(() => {
if(this.status === Commitment.REJECTED) {
this.status = Commitment.REJECTED
this.result = result
this.rejectCallbacks.forEach(callback => {
callback(result)
})
}
})
}
then(onFULFILLED, onREJECTED) {
return new Commitment((resolve, reject) => {
onFULFILLED = typeof onFULFILLED === 'function' ? onFULFILLED : () => {}
onREJECTED = typeof onFULFILLED === 'function' ? onREJECTED : () => {}
if(this.status === Commitment.PENDING) {
this.rejectCallbacks.push(onREJECTED)
this.resolveCallbacks.push(onFULFILLED)
}
if(this.status === Commitment.FULFILLED) {
setTimeout(() => {
onFULFILLED(this.result)
})
}
if(this.status === Commitment.REJECTED) {
setTimeout(()=> {
onREJECTED(this.result)
})
}
})
}
}
let commitment = new Commitment((resolve, reject) => {
})
