forEach 遍历

const nums = [1, 2, 3, 4, 5];
nums.forEach(function(item, index, array) {
    console.log(item);
})

map 返回新数组

const result = nums.map(function(item, index, array) {
    return item * 2;
})
console.log(result);

filter 过滤

const result = nums.filter(function(item, index, array) {
    return item % 2 == 0;
})
console.log(result)