Javascript一些对象
返回指定位置的字符
charAt();
//实例
let sum = "abcd";
sum.charAt(1);
//b
连接字符串,并返回新字符串
concat();
let sum = "123";
let num = "456";
sum.concat(num)
//123456
返回指定字符的位置
//返回时如果字符串中没有你设置返回的字符,则返回-1
indexOf();
let sum = "abcd"
sum.indexOf("c")
//2
复制字符次数,并返回一个新的字符串
repeat();
let sum = "123";
sum.repeat(3);
//123123123
查找与正则表达式匹配的值
search();
let sum = "hello brother";
sum.search("brother")
//6
截取字符串,并以新字符串返回
slice();
let sum = "This is a paragraph";
sum.slice(5,9);
//is a
把字符串分割为字符串数组
split();
let sum = "This is a paragraph";
sum.split(" ");
//This,is,a,paragraph
从索引提取字符串指定数目字数
substr();
let sum = "This is a paragraph";
sum.substr(10,9);
//paragraph
转小写
toLowerCase();
let sum = "ABC";
sum.toLowerCase();
//abc
转大写
toUpperCase();
let sum = "abc";
sum.toUpperCase();
//ABC
