title: Javascript const with curly braces which have 2 variable separated by colon
body: <p>I'm working on a react native project, I found a solution on internet to my problem but I don't understand one line from a function</p>
  
  <pre><code>componentDidUpdate(propsOld) { // line 1
      const { fill } = this.props;  // line 2
      const { fill:fillOld } = propsOld; // line 3
  
      if (fill !== fillOld) { // line 4
        Animated.timing(this.anim, { toValue:fill, duration:2000 // line 5 }).start();
      }
  }
  </code></pre>
  
  <p>The line that I don't understand is the line 3:</p>
  
  <p><code>const { fill:fillOld } = propsOld;</code></p>
  
  <p>I understand the use of curly braces when there is a single variable or multiple variables seperated by comma ',',</p>
  
  <p>Would anyone please explain to me the meaning when they are separated by colon ':' ?</p>