Added solution and fix tests

Author: UmiKami

exercises/100-getAverageOfElementsAtProperty/solutiuon.hide.js

@@ -0,0 +1,14 @@
+  // your code here
+  function getAverageOfElementsAtProperty(obj, key){
+    if(!obj[key] || !Array.isArray(obj[key]) || obj[key].length == 0){
+        return 0;
+    }
+    
+    let sum = 0;
+
+    for (let i = 0; i < obj[key].length; i++) {
+      sum+=obj[key][i] 
+    }
+
+    return sum / obj[key].length;
+}

exercises/100-getAverageOfElementsAtProperty/test.js

@@ -39,7 +39,7 @@ test('If the property at the given key is not an array, it should return 0', ()
 
 test('If there is no property at the given key, it should return 0', () => {
   let obj = {};
-  let output = getAverageOfElementsAtProperty(obj['key']);
+  let output = getAverageOfElementsAtProperty(obj, "key");
   expect(output).toBe(0);
 });