var content = "12345,abcde";
var num = content.substring(0,5);//12345
var letter = content.substring(7,11);//abcde
var i = content.indexof(","); //6
var data = content.substring(i+1,content.length);//abcde
content = content.replace("123","aaa"); //content = "aaa45,abcde"; (未做全局替换)