// https://tc39.github.io/ecma262/#sec-array.prototype.includes
if (!Array.prototype.includes) {
	Object.defineProperty(Array.prototype, "includes", {
		value: function(searchElement, fromIndex) {

			// 1. Let O be ? ToObject(this value).
			if (this == null) {
				throw new TypeError("\"this\" is null or not defined");
			}

			var o = Object(this);

			// 2. Let len be ? ToLength(? Get(O, "length")).
			var len = o.length >>> 0;

			// 3. If len is 0, return false.
			if (len === 0) {
				return false;
			}

			// 4. Let n be ? ToInteger(fromIndex).
			//    (If fromIndex is undefined, this step produces the value 0.)
			var n = fromIndex | 0;

			// 5. If n ≥ 0, then
			//  a. Let k be n.
			// 6. Else n < 0,
			//  a. Let k be len + n.
			//  b. If k < 0, let k be 0.
			var k = Math.max(n >= 0 ? n : len - Math.abs(n), 0);

			// 7. Repeat, while k < len
			while (k < len) {
				// a. Let elementK be the result of ? Get(O, ! ToString(k)).
				// b. If SameValueZero(searchElement, elementK) is true, return true.
				// c. Increase k by 1.
				// NOTE: === provides the correct "SameValueZero" comparison needed here.
				if (o[k] === searchElement) {
					return true;
				}
				k++;
			}

			// 8. Return false
			return false;
		}
	});
}