title: Use Lo-Dash merge without modifying underlying object
body: <p>How can I use lodash <code>_.merge(obj, source)</code> without <code>obj</code> being modified? I just want a return of the value that merge computes,but I want to keep my original object intact.</p>
  
  <p>I assume this question applies to most lodash functions, but I haven't found a solution so far.</p>