JSFiddle - React, Tailwind, and code Playground

HTML

<input type='text' id='textboxId' value='2014/09/01'>

JavaScript

(function ($, undefined) {
    $.fn.getCursorPosition = function() {
        var el = $(this).get(0);
        var pos = 0;
        if('selectionStart' in el) {
            pos = el.selectionStart;
        } else if('selection' in document) {
            el.focus();
            var Sel = document.selection.createRange();
            var SelLength = document.selection.createRange().text.length;
            Sel.moveStart('character', -el.value.length);
            pos = Sel.text.length - SelLength;
        }
        return pos;
    }
})(jQuery);

$("#textboxId").keydown(function(e){
    var currentPos=$(this).getCursorPosition();
    var lastChar=$(this).val().substr((currentPos- $(this).val().length)- 1);
    if(e.which==8 && lastChar.match(/^\//g) ){
        e.preventDefault();
        return false;
    }
});