class Promise {
    constructor(executor) {
        executor(this.resolve, this.reject);
    }
    // 状态
    status = "PENDING";
    // 返回的结果
    value = undefined;
    //成功的回调
    onfulfilled = [];
    //失败的回调
    onrejected = [];
    resolve = (value) => {
        if (this.status === "PENDING") {
            this.status = "FULFILLED";
            this.value = value;
            this.onfulfilled.forEach((item) => item(value));
        }
    };
    reject = (value) => {
        if (this.status === "PENDING") {
            this.status = "REJECTED";
            this.value = value;
            this.onrejected.forEach((item) => item(value));
        }
    };
    then = (onfulfilled, onrejected) => {
        if (this.status === "FULFILLED") {
            onfulfilled(this.value);
        } else if (this.status === "REJECTED") {
            onrejected(this.value);
        } else if (this.status === "PENDING") {
            this.onfulfilled.push(onfulfilled);
            this.onrejected.push(onrejected);
        }
    };
}