对象和数组通用forEach

forEach

function forEach(target, iteratee) {
    const array = Array.isArray(target) ? target : Object.keys(target);
    let index = -1;
    const length = array.length;
    while (++index < length) {
        const key =  target !== array ? array[index] : index;
        iteratee(target[key], key);
    }
    return target;
}
//使用方式
const target = [1,3,4];
const target1 = {a:'2',b:'3'};

forEach(target,(value,key)=>{
  console.log(value,key)
})