数组知识点
map forEach filter slice find concat findIndex includes
indexOf isArray join lastIndexOf reduce some toString valueOf every 不会改变原始数组
fill push pop unshift shift reverse sort splice copyWithin 改变原数组
map filter slice concat 返回一个新数组 不会改变原始数组
数组知识点
map forEach filter slice find concat findIndex includes
indexOf isArray join lastIndexOf reduce some toString valueOf every 不会改变原始数组
fill push pop unshift shift reverse sort splice copyWithin 改变原数组
map filter slice concat 返回一个新数组 不会改变原始数组