javascript 字符串

//返回指定位置字符charAt：
var mystr="I love you!";
console.log(mystr.charAt(3)); 
//"o"

//返回字符串首次出现位置indexOf：
var mystr="I love you!";
console.log(mystr.indexOf("o")); 
//3
console.log(mystr.indexOf('o',4));
//-1

//截取字符串substring:
var mystr='ceshi yixia'；
console.log(mystr.substring(2,2));
//""
console.log(mystr.substring(2,5));
//"shi"
console.log(mystr.substring(5,2));
//"shi"

//指定截取长度substr:
var mystr="Hello World!";
console.log(  mystr.substr(6,5));
//World
console.log( mystr.substr(0,5));
//Hello

//字符串反序
var str="i love you";
str.split('').reverse().join('');
//uoy evol i