What's the best way to automatically insert slashes '/' in date fields

Question

I\'m trying to add functionality to input date fields so as when the users enters in digits, slashes \"/\" get automatically added.

So suppose I have the following

Answer 1

If you're looking for pure js version of @Chris's answer

var newInput = document.getElementById("theDate");
newInput.addEventListener('keydown', function( e ){
    if(e.which !== 8) {
        var numChars = e.target.value.length;
        if(numChars === 2 || numChars === 5){
            var thisVal = e.target.value;
            thisVal += '/';
            e.target.value = thisVal;
        }
    }
});

And HTML section might be(if necessary):