Add all the A tasks

Task/Averages-Median/JavaScript/averages-median.js

@@ -0,0 +1,15 @@
+function median(ary) {
+    if (ary.length == 0)
+        return null;
+    ary.sort(function (a,b){return a - b})
+    var mid = Math.floor(ary.length / 2);
+    if ((ary.length % 2) == 1)  // length is odd
+        return ary[mid];
+    else
+        return (ary[mid - 1] + ary[mid]) / 2;
+}
+
+median([]);   // null
+median([5,3,4]);  // 4
+median([5,4,2,3]);  // 3.5
+median([3,4,1,-8.4,7.2,4,1,1.2]);  // 2.1