Contains Duplicate solution

Author: kim-young

contains-duplicate/kimyoung.js

@@ -0,0 +1,10 @@
+var containsDuplicate = function (nums) {
+  let set = new Set(); // create a set to keep track of items within the nums array
+  for (const el of nums) set.add(el); // add items to the set, duplicates will automatically be ignored (set vs map)
+  return set.size !== nums.length; // compare the length of nums array and the size of the set, which shows if there's a duplicate or not
+};
+
+// test cases
+console.log(containsDuplicate([])); // false
+console.log(containsDuplicate([1, 2, 3, 1])); // true
+console.log(containsDuplicate([1, 2, 3, 4])); // false