This function takes a date object as a parameter and returns a string in MM/DD/YYYY format :
function format(date) {
    return [
        ('0' + (date.getMonth() + 1)).slice(-2),
        ('0' + date.getDate()).slice(-2),
        date.getFullYear()
    ].join('/')
}
Usage example (gives today's date in MM/DD/YYYY format) :
format(new Date) // "01/03/2014"
You can easily change the resulting format with a few modifications :
function format(date) {
    return [
        date.getDate(),
        date.getMonth() + 1,
        ('' + date.getFullYear()).slice(-2)
    ].join('-')
}
Usage example (gives today's date in D-M-YY format) :
format(new Date) // "3-1-14"
Playing around
I've tuned the function a bit, this might be interesting for very basic needs :)
function format(date, format) {
    var i = 0, bit;
    if (!format) format = 'MM/DD/YYYY'; // default
    format = format.split(/([^DMY]+)/i);
    while (bit = format[i]) {
        switch (bit.charAt(0).toUpperCase()) {
            case 'D': format[i] = date.getDate(); break;
            case 'M': format[i] = date.getMonth() + 1; break;
            case 'Y': format[i] = date.getFullYear(); break;
        }
        if (bit.length === 2) {
            format[i] = ('0' + format[i]).slice(-2);
        }
        i += 2;
    }
    return format.join('');
}
Usage examples :
format(new Date)             // "01/03/2014" (default)
format(new Date, 'd/m/y')    // "3/1/2014"
format(new Date, 'D/M/Y')    // "3/1/2014"
format(new Date, 'DD-MM-YY') // "03-01-14"
format(new Date, 'M/YY')     // "1/14"