title: Add multiple styling class to object on React Material-UI
body: <p>I have JSX like this:</p>
  <pre><code> &lt;span className=&quot;btn-pause btn&quot;&gt;&lt;i class=&quot;fa fa-pause&quot;&gt;&lt;/i&gt;&lt;/span&gt;
  </code></pre>
  <p>Now I want to change the color of this button:</p>
  <pre><code>const styles = {
     btncolor:{
        backgroundColor:&quot;#0E122D&quot;
     }
  }
  const useStyles = makeStyles(styles)
  </code></pre>
  <p>How should I add this style to <code>className</code> with normal other class?</p>
  <pre><code> &lt;span className=&quot;btn-pause btn {{classes.btncolor}}&quot;&gt;&lt;i className=&quot;fa fa-pause&quot;&gt;&lt;/i&gt;&lt;/span&gt;
  </code></pre>
  <p>It doesn't work.</p>