1. Promise.all实现

    Promise.all =  function(promises) {
        var values = new Array(promises.length); // 保存成功value的数组
        var resolvedCount = 0;
        return new Promise((resolve, reject) => {
            promises.forEach((p, index) => {
                Promise.resolve(p).then(
                    value => {
                        resolvedCount ++;
                        values[index] = value;
                        if (resolvedCount === promises.length) {
                            resolve(values);
                        }
                    },
                    reason => {
                        reject(reason);
                    }
                )
            })
        })
    }

2. Promise.race实现

    Promise.race = function(promises) {
        return new Promise((resolve, reject) => {
            promises.forEach((p, index) => {
                Promise.resolve(p).then(
                    value => {
                        resolve(value);
                    },
                    reason => {
                        reject(reason)
                    }
                )
            })
        })
    }