Apply more let/const transforms.

_compareMultiple.js

@@ -15,19 +15,19 @@ import compareAscending from './_compareAscending.js';
  * @returns {number} Returns the sort order indicator for `object`.
  */
 function compareMultiple(object, other, orders) {
-  var index = -1,
-      objCriteria = object.criteria,
-      othCriteria = other.criteria,
-      length = objCriteria.length,
-      ordersLength = orders.length;
+  let index = -1;
+  const objCriteria = object.criteria;
+  const othCriteria = other.criteria;
+  const length = objCriteria.length;
+  const ordersLength = orders.length;
 
   while (++index < length) {
-    var result = compareAscending(objCriteria[index], othCriteria[index]);
+    const result = compareAscending(objCriteria[index], othCriteria[index]);
     if (result) {
       if (index >= ordersLength) {
         return result;
       }
-      var order = orders[index];
+      const order = orders[index];
       return result * (order == 'desc' ? -1 : 1);
     }
   }