Given a string containing letters and + characters implement a function which determines if each letter in the string is surrounded by + character. There may be more than one + character between letters (+a++b+) and letters may be surrounded by the same + character (+a+b+).

Challenge | Solution

surroundedLetter("+a+") // true

surroundedLetter("+ab+") // false

surroundedLetter("+a+b+") // true

surroundedLetter("+a++b++") // true