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| class MyPromise {
constructor(fn) {
fn(value=>this.cb?.(value))
}
then(fn) {
return new MyPromise(res=>this.cb = val=>{
const thenCb = fn(val)
thenCb instanceof MyPromise ? thenCb.then(res) : res(thenCb)
})
}
}
new MyPromise((resolve)=>{
setTimeout(()=>{
resolve(1)
}, 1000)
}
).then((res)=>{
console.log(res)
return new MyPromise((resolve)=>{
setTimeout(()=>{
resolve(2)
}, 1000)
})
}
).then(res=>{
console.log(res)
})
|
