- Had to google how sqrt is actually calculated T_T .

_013_sqrt.js

@@ -0,0 +1,15 @@
+/**
+ * @param {number} x
+ * @return {number}
+ */
+var mySqrt = function(x) {
+    if(x<2) return x;
+
+    let r = x;
+
+    while (r * r > x) {
+        r = Math.floor((r + x / r) / 2);
+    }
+
+    return r;
+};