Remove double Charaters (Beware of the spaces!!!)

trimDoubleChars.js

function removeDoubleChars(){
    var input = document.getElementById('inputText').value,
        output = document.getElementById('outputText'),
        chars = [];
    for(var i = 0; i < input.length; i++){
        if(chars.indexOf(input[i]) === -1) chars.push(input[i]);
    }
    chars.sort();
    output.value = chars.join('');
};