lib/index.js
function DoubleLast(input, letters) {
    var last = LastChar(input);
    if (!letters || ~letters.indexOf(last)) {
        return input + last;
    }
    return input;
}
function DoubleLast(input, letters) {
    var last = LastChar(input);
    if (!letters || ~letters.indexOf(last)) {
        return input + last;
    }
    return input;
}
function DoubleLast ( input , letters ) { var last = LastChar ( input ) ; if ( ! letters || ~ letters . indexOf ( last ) ) { return input + last ; } return input ; }
DoubleLast
Doubles the last letter.

@name DoubleLast
@function
@param {String} input The input string.
@param {Array} letters An array of letters: if the last letter of the input
is not found in this list, it will *not* be doubled.
@return {String} The modified string.
DoubleLast Doubles the last letter .