Get Substring between two characters using javascript (ok)

https://stackoverflow.com/questions/14867835/get-substring-between-two-characters-using-javascript

Current

Str = 'MyLongString:StringIWant;'

Desired Output

newStr = 'StringIWant'

Answers

var mySubString = str.substring(
    str.lastIndexOf(":") + 1, 
    str.lastIndexOf(";")
);