Titleize a sentence in JavaScript

titleize.js

function titleize(sentence) {
    if(!sentence.split) return sentence;
    var _titleizeWord = function(string) {
            return string.charAt(0).toUpperCase() + string.slice(1).toLowerCase();
        },
        result = [];
    sentence.split(" ").forEach(function(w) {
        result.push(_titleizeWord(w));
    });
    return result.join(" ");
}