title: Merge two objects with override in javascript
body: <p>I want to merge two objects, override properties but keep properties that are not been overridden.</p>
  
  <p>Example: I have the following Objects</p>
  
  <pre><code>const theme = {
   colors: {
    base: '#fff',
    accent: '#ff0000'
   }
  }
  </code></pre>
  
  <p>and </p>
  
  <pre><code>const themeOverride = {
   colors: {
    accent: '#ff8900'
   }
  }
  </code></pre>
  
  <p>and would like to merge these together to get</p>
  
  <pre><code>const newTheme = {
    colors: {
     base: '#fff',
     accent: '#ff8900'
    }
  }
  </code></pre>