Interview question: javascript implement promise A+ standard, pass promises-aplus-tests

/**
 * Promise A+ standard implementatio
 * pass promises-aplus-tests
 */
var PENDING = "pending"
var FULFILLED = "fulfilled"
var REJECT = "rejected"
var id = 0
module.exports = class Promise {
    constructor(todo) {
        this.id = id
        // use id distinct diff promise when debug
        id += 1
        todo(this.resolve.bind(this), this.reject.bind(this))
    }
    used = false
    status = PENDING
    value = null
    reason = null
    onFulfilleds = []
    onRejects = []
    resolve(value) {
        if (this.status == PENDING) {
            if (this.onFulfilleds.length > 0) {
                // console.log(`this.id:${this.id} resolve`);
            }
            this.status = FULFILLED
            this.value = value
            this.onFulfilleds.forEach((fn) => {
                fn(value);
            })
        }
    }
    reject(reason) {
        if (this.status == PENDING) {
            this.status = REJECT
            this.reason = reason
            this.onRejects.forEach((fn) => {
                fn(reason)
            })
        }
    }
    then(onFulfilled, onRejected) {
        if (typeof onFulfilled != "function") {
            onFulfilled = (value) => {
                return value
            }
        }
        if (typeof onRejected != "function") {
            onRejected = (reason) => {
                throw reason
            }
        }
        var p2 = new Promise((resolve, reject) => {
                var asyncAndCatch = (fn) => {
                    setTimeout(() => {
                        try {
                            var r = fn()
                            this.resolvePromise(p2, r, resolve, reject)
                        } catch (e) {
                            reject(e)
                        }
                    })
                }
                if (this.status == PENDING) {
                    // console.log(`this.id:${this.id} push`)
                    this.onFulfilleds.push((value) => {
                        asyncAndCatch(() => {
                            return onFulfilled(value)
                        })
                    });
                    this.onRejects.push((reaons) => {
                        asyncAndCatch(() => {
                            return onRejected(reaons)
                        })
                    });
                } else {
                    if (this.status == FULFILLED) {
                        asyncAndCatch(() => {
                            return onFulfilled(this.value)
                        })
                    } else if (this.status == REJECT) {
                        asyncAndCatch(() => {
                            return onRejected(this.reason)
                        })
                    }
                }
            }
        )
        return p2
    }
    resolvePromise(p2, result, resolve, reject) {
        if (p2 == result) {
            throw new TypeError("Chain cycle")
        }
        if (result /* typeof null == "object", so `result &&` to make sure result has value*/
            && (typeof result == "object" || typeof result == "function")) {
            var used
            try {
                var then = result.then;
                if (typeof then == "function") {
                    then.call(result, (val) => {
                        if (used) return
                        used = true
                        this.resolvePromise(p2, val, resolve, reject)
                    }, (reason) => {
                        if (used) return
                        used = true
                        reject(reason)
                    })
                } else {
                    if (used) {
                        return
                    }
                    used = true
                    resolve(result)
                }
            } catch (e) {
                if (used) {
                    return
                }
                used = true
                reject(e)
            }
        } else {
            // console.log(`caller.id:${this.id}`)
            resolve(result)
        }
    }
}

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