数组遍历

const nameArray2 = ['zhao', 'qian', 'zhang', 'sun', 'li'];
nameArray2.map(() => {}); // return
const filterResult = nameArray2.filter((value) => {return value === 'zhang';
}); // return array
nameArray2.forEach(() => {}); // no return

对象遍历

Object.keys(object).map/forEach/filter...