手写Promise

function Promise(executor) {
    this.status = 'pending';
    this.data = '';
    this.reason = '';
    this.fn1CallBacks = [];
    this.fn2CallBacks = [];

    let resolve = value => {
        if (this.status === 'pending') {
            this.status = 'fulfilled';
            this.data = value;
            for (var i = 0; i < this.fn1CallBacks.length; i++) {
                self.fn1CallBacks[i](value)
            }
        }
    };  

    let reject = reason => {
        if (this.status === 'pending') {
            this.status = 'reject';
            this.reason = reason;
            for (var i = 0; i < this.fn2CallBacks.length; i++) {
                self.fn2CallBacks[i](reason)
            }
        }
    };

    try {
        executor(resolve,reject)
    } catch (err) {
        reject(err)
    }
}

Promise.prototype.then = function(fn1,fn2) {
    var self = this;
    var promise2;

    fn1 = type fn1 === 'function' ? fn1 : function(v) {};
    fn2 = type fn2 === 'function' ? fn2 : function(r) {};

    if (self.status === 'resolved') {
        return promise2 = new Promise(function(resolve,reject) {
            try {
                var x = fn1(self.data);
                resolve(x)
            } catch(err) {
                reject(err)
            }
        })
    }

    if (self.status === 'reject') {
        return promise2 = new Promise(function(resolve,reject) {
            try {
                var x = fn2(self.data);
                reject(x)
            } catch(err) {
                reject(err)
            }
        })
    }

    if (self.status === 'pending') {
        return promise2 = new Promise(function(resolve,reject) {
            this.fn1CallBacks.push(function(value) {
                try {
                    var x = fn1(self.data);
                    resolve(x)
                } catch(err) {
                    reject(err)
                }
            })

            this.fn2CallBacks.push(function(value) {
                try {
                    var x = fn2(self.data);
                    reject(x)
                } catch(err) {
                    reject(err)
                }
            })

        })
    }
}