js 字符串转整型，数字转字符串，字符串截取，字符串转数组，数组转字符串

字符串转整型

var str = "23";
str = parseInt(str);
console.log(str);

数字转字符串

var str = 23;
str = str + '';
console.log(str)

字符串截取

var str = '2021-04-03 12:12:12';
str = str.substr(0,10);
console.log(str)
//输出 2021-04-03

//获取后缀名
var str = 'index.html';
str = str.substr(str.lastIndexOf('.')+1);
console.log(str);
//输出html

字符串转数组

var str= '123,456,789';
var arr= str.split(',');

数组转字符串

var arr = [1,2,3,4,5]; 
var str = a.join(",");