javascript-手写实现reduce

简单实现reduce方法

Array.prototype._reduce = function (Fn, initialValue) {
    if (typeof Fn !== 'function') {
        throw new TypeError('first param is not a function');
    }
    const arr = this
    let result = initialValue;
    for (let i = 0; i < arr.length; i++) {
        result = Fn(result, arr[i], i);
    }
    return result
}
const result = [1, 2, 3]._reduce((result, item, index) => {
    return result += item
}, 0)
console.log(result) // 6