编辑代码

const arr = [1, 2, 3, 4];
Array.prototype.myReduce = function(func, initial) {
    let result = initial;
    for (let i = 0; i < this.length; i++) {
        result = func(result, this[i]);
    }
    return result;
}
console.log(arr.myReduce((l,r) => l + r, 2)); // 12