Avoid terminal equality checks in array mode

Author: kpdecker

src/diff/base.js

@@ -145,9 +145,6 @@ Diff.prototype = {
 
   equals(left, right) {
     if (this.options.comparator) {
-      if (Array.isArray(right)) {
-        right = right[0];
-      }
       return this.options.comparator(left, right);
     } else {
       return left === right
@@ -215,10 +212,12 @@ function buildValues(diff, components, newString, oldString, useLongestToken) {
     }
   }
 
-  // Special case handle for when one terminal is ignored. For this case we merge the
-  // terminal into the prior string and drop the change.
+  // Special case handle for when one terminal is ignored (i.e. whitespace).
+  // For this case we merge the terminal into the prior string and drop the change.
+  // This is only available for string mode.
   let lastComponent = components[componentLen - 1];
   if (componentLen > 1
+      && typeof lastComponent.value === 'string'
       && (lastComponent.added || lastComponent.removed)
       && diff.equals('', lastComponent.value)) {
     components[componentLen - 2].value += lastComponent.value;