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Copy pathpromise4.js
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41 lines (38 loc) · 1.1 KB
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/**
* Created by wyw on 2018/12/17.
*/
function Promise(fn){
this.resolves = [];
this.status = 'PENDING';
this.value;
this.then = (onFulfilled) => {
if (this.status === 'PENDING') {
this.resolves.push(onFulfilled);
} else if (this.status === 'FULFILLED') {
console.log('isFULFILLED');
onFulfilled(this.value);
}
return this;
};
let resolve = (value) =>{
if (this.status === 'PENDING') {
setTimeout(_ => {
this.status = 'FULFILLED';
this.resolves.forEach(fn => value = fn(value) || value);
this.value = value;
});
}
};
fn(resolve);
}
let getInfor = new Promise((resolve, reject) => {
resolve('success');
}).then(r => {
console.log('hahah');
});
setTimeout(_ => {
getInfor.then(r => {
console.log(r);
})
});
//现在我们在then方法中return的是他本身，这样一来所有的操作都是在一个Promise上，而Promise的状态又是不能随意转化的，所以都是以第一个Promise的状态为准