Only copy old/new code when selecting left/right side of parallel diff

1 files changed, 14 insertions, 1 deletions

diff --git a/app/assets/javascripts/diff.js b/app/assets/javascripts/diff.js
index 6a008112203..ae8338f5fd2 100644
--- a/app/assets/javascripts/diff.js
+++ b/app/assets/javascripts/diff.js
@@ -24,7 +24,8 @@ class Diff {
     if (!isBound) {
       $(document)
         .on('click', '.js-unfold', this.handleClickUnfold.bind(this))
-        .on('click', '.diff-line-num a', this.handleClickLineNum.bind(this));
+        .on('click', '.diff-line-num a', this.handleClickLineNum.bind(this))
+        .on('mousedown', 'td.line_content.parallel', this.handleParallelLineDown.bind(this));
       isBound = true;
     }
 
@@ -100,6 +101,18 @@ class Diff {
     this.highlightSelectedLine();
   }
 
+  handleParallelLineDown(e) {
+    const line = $(e.currentTarget);
+    const table = line.closest('table');
+
+    table.removeClass('left-side-selected right-side-selected');
+
+    const lineClass = ['left-side', 'right-side'].filter(name => line.hasClass(name))[0];
+    if (lineClass) {
+      table.addClass(`${lineClass}-selected`);
+    }
+  }
+
   diffViewType() {
     return $('.inline-parallel-buttons a.active').data('view-type');
   }