字符串大写转小写 let str = "What is 爱马仕? That is not doing. 就问你这个英语溜不溜。……&*%*" console.log(str.toLowerCase()) 字符串小写转大写 let str = "What is 爱马仕? That is not doing. 就问你这个英语溜不溜。……&*%*" console.log(str.toUpperCase())