filter 过滤器 和 zip 合并数组

filter

一个简单的过滤器, 因为 for of ,使得其可以适用于数组和对象

_.filter = (array,fn)=>{
            let results = [];
            for(const value of array){
                    (fn(value)) ? results.push(value) : undefined;
            }
            return results;
    }

zip

按照相应传入的fn规则合并对应数组

_.zip = (leftArr,rightArr,fn)=>{
            let index,len,result = [];
            let [leftArrLen,rightArrLen] = [leftArr.length,rightArr.length];
            for(index = 0,len = Math.min(leftArrLen,rightArrLen);index<len;index++){
                    result.push(fn(leftArr[index],rightArr[index]));
            }

            //如果两个数组长度不同，直接在result后面加上多出部分数组
            if(leftArrLen > rightArrLen){
                    result = result.concat(leftArr.slice(rightArrLen,leftArrLen));
            }else if(leftArrLen < rightArrLen){
                    result = result.concat(rightArr.slice(leftArrLen,rightArrLen));
            }
            return result;
    }

示例:

let a = [1,2,3,4];
let b = [2,1,2];
console.log(_.zip(a,b,(l,r)=>l+r)); // [ 3, 3, 5, 4 ]