title: Inclusive mixin with JS
body: <p>So I want to prevent overriding shared keys, when doing a mixin with JS, so we have:</p>
  
  <pre><code>const v = {
    a: {
      b: {
        c: 4,
        d: 'str'
      }
    }
  };
  
  
  console.log(Object.assign({}, v, {a: {b: {c: 5}}}));
  </code></pre>
  
  <p>this will log:</p>
  
  <blockquote>
    <p>{ a: { b: { c: 5 } } }</p>
  </blockquote>
  
  <p>but I am looking for this instead:</p>
  
  <blockquote>
    <p>{ a: { b: { c: 5, d: 'str' } } }</p>
  </blockquote>
  
  <p>anyone know how to do this (preferably without a library).</p>