add raid at test and implementation b00tc4mp#160

staff/manuel-barzi/playground/raids/Raid.prototype.at.js

@@ -0,0 +1,25 @@
+var Raid = function () {
+    this.length = 0
+}
+
+Raid.prototype.at = function (index) {
+    var element = this[index]
+
+    return element
+}
+
+console.log('TEST Raid.prototype.at')
+
+console.log('CASE get number at index 3 in nums')
+
+var nums = new Raid
+nums[0] = 100
+nums[1] = 200
+nums[2] = 300
+nums[3] = 400
+nums[4] = 500
+nums.length = 5
+
+var num = nums.at(3)
+console.log(num)
+// 400