indexOf
"APPLE&LEMON".indexOf("APPLE") = 0
-1 没有在里面
substr
substr(开始位置,截取长度)
replace
“helloworld”.replace(“world”,”apple”) = “helloapple”
toUpperCase
”“.toUpperCase 全大写
toLowerCase
首字母大写其他小写
split
“apple/banana”.split(“/”) = [“apple”,”banana”]
join
[“apple”,”lemon”].join(“+”) = “apple+lemon”