关于javascript:手写一个promise的过程一

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const PEDDING = 'PEDDING';
const RESOLVE = 'RESOLVE';
const REJECT = 'REJECT';
// promise 有三种状态
class NewPromise {
// 初始状态为 PEDDING
    status = PEDDING
    result = undefined;
    reason = undefined;
    // 公布订阅者模式
    // 目标是为了实现异步
    onResolveArr = [];
    onRejectArr = [];
    constructor(exc) {
        const resolve = result => {if (this.status === PEDDING) {
                this.result = result
                this.status = RESOLVE
                // 执行订阅者
                this.onResolveArr.map(fn => fn())
            }
        }
        const reject = reason => {if (this.status === PEDDING) {
                this.reason = reason
                this.status = REJECT
                // 执行订阅者
                this.onRejectArr.map(fn => fn())
            }
        }
        exc(resolve, reject)

    }

    then(onResolve, onReject) {if (this.status === RESOLVE) {setTimeout(() => {onResolve(this.result)
            }, 0)
        }
        if (this.status === REJECT) {setTimeout(() => {onReject(this.reason)
            }, 0)
           
        }
        // 公布订阅者模式
        if (this.status === PEDDING) {
            // 将发布者增加到数组外面
            this.onResolveArr.push(() => {onResolve(this.result)
            })
            this.onRejectArr.push(() => {this.onReject(this.reason)
            })

        }
    }
}


// let yan = new Promise((resole, reject) => {//     resole('闫大爷真帅')
// })
// yan.then(res => {//     console.log(res)
// })

let newYan = new NewPromise((resole, reject) => {setTimeout(()=>{resole('new 闫大爷真帅')
    },3000)
    
})
newYan.then(res => {console.log(res)
})

console.log(11111111)

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