freeCodeCamp.org React: Optimize Re-Renders with shouldComponentUpdate 35/47

Objective:

So far, if any component receives new state or new props, it re-renders itself and all its children. This is usually okay. But React provides a lifecycle method you can call when child components receive new state or props, and declare specifically if the components should update or not. The method is shouldComponentUpdate(), and it takes nextProps and nextState as parameters.
This method is a useful way to optimize performance. For example, the default behavior is that your component re-renders when it receives new props, even if the props haven’t changed. You can use shouldComponentUpdate() to prevent this by comparing the props. The method must return a boolean value that tells React whether or not to update the component. You can compare the current props (this.props) to the next props (nextProps) to determine if you need to update or not, and return true or false accordingly.

The shouldComponentUpdate() method is added in a component called OnlyEvens. Currently, this method returns true so OnlyEvens re-renders every time it receives new props. Modify the method so OnlyEvens updates only if the value of its new props is even. Click the Add button and watch the order of events in your browser’s console as the lifecycle hooks are triggered.

Solution:

All you need to know is how to check if number is even. Little search in your favourite search engine gives you formula:

n % 2 == 0

With this we can start if statement checking whether nextProps.value divides by 2 or not and return true or false accordingly:

     if(nextProps.value% 2 == 0)
    {
      return true;
    }else{
      return false;
    }

It works!