Date Evaluation in JS

Question

I need to validate a credit card expiry date, I have the javascript code but I don't know how to customize it for my need.

this is my code, I only need the date in a mm/yy format but this code has the date format in mm/dd/yyyy.

var date = document.getElementById('date');

    function checkValue(str, max) {
      if (str.charAt(0) !== '0' || str == '00') {
        var num = parseInt(str);
        if (isNaN(num) || num <= 0 || num > max) num = 1;
        str = num > parseInt(max.toString().charAt(0)) 
               && num.toString().length == 1 ? '0' + num : num.toString();
      };
      return str;
    };

    date.addEventListener('input', function(e) {
      this.type = 'text';
      var input = this.value;
      if (/\D\/$/.test(input)) input = input.substr(0, input.length - 3);
      var values = input.split('/').map(function(v) {
        return v.replace(/\D/g, '')
      });
      if (values[0]) values[0] = checkValue(values[0], 12);
      if (values[1]) values[1] = checkValue(values[1], 31);
      var output = values.map(function(v, i) {
        return v.length == 2 && i < 2 ? v + ' / ' : v;
      });
      this.value = output.join('').substr(0, 14);
    });