polyfill.js

if (!Array.prototype.find) {
  Object.defineProperty(Array.prototype, 'find', {
    enumerable: false,
    configurable: true,
    writable: true,
    value: function(predicate) {
      if (this == null) {
        throw new TypeError('Array.prototype.find called on null or undefined');
      }
      if (typeof predicate !== 'function') {
        throw new TypeError('predicate must be a function');
      }
      var list = Object(this);
      var length = list.length >>> 0;
      var thisArg = arguments[1];
      var value;

      for (var i = 0; i < length; i++) {
        value = list[i];
        if (predicate.call(thisArg, value, i, list)) {
          return value;
        }
      }
      return undefined;
    }
  });
}
if (!Array.prototype.fill) {
    Object.defineProperty(Array.prototype, 'fill', {
        enumerable: false,
        configurable: true,
        writable: true,
        value:  function(value) {
            // Steps 1-2.
            if (this == null) {
                throw new TypeError("this is null or not defined");
            }

            var O = Object(this);

            // Steps 3-5.
            var len = O.length >>> 0;

            // Steps 6-7.
            var start = arguments[1];
            var relativeStart = start >> 0;

            // Step 8.
            var k = relativeStart < 0 ?
                Math.max(len + relativeStart, 0) :
                Math.min(relativeStart, len);

            // Steps 9-10.
            var end = arguments[2];
            var relativeEnd = end === undefined ?
                len : end >> 0;

            // Step 11.
            var final = relativeEnd < 0 ?
                Math.max(len + relativeEnd, 0) :
                Math.min(relativeEnd, len);

            // Step 12.
            while (k < final) {
                O[k] = value;
                k++;
            }

            // Step 13.
            return O;
        }
    });
}
if (!Array.prototype.findIndex) {
    Object.defineProperty(Array.prototype, 'findIndex', {
        enumerable: false,
        configurable: true,
        writable: true,
        value: function(predicate) {
            if (this == null) {
                throw new TypeError('Array.prototype.find called on null or undefined');
            }
            if (typeof predicate !== 'function') {
                throw new TypeError('predicate must be a function');
            }
            var list = Object(this);
            var length = list.length >>> 0;
            var thisArg = arguments[1];
            var value;

            for (var i = 0; i < length; i++) {
                value = list[i];
                if (predicate.call(thisArg, value, i, list)) {
                    return i;
                }
            }
            return -1;
        }
    });
}

if ( !String.prototype.contains ) {
    String.prototype.contains = function() {
        return String.prototype.indexOf.apply( this, arguments ) !== -1;
    };
}