React: update one item in a list without recreating all items

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You can do it by using any state management library, so that your Parent doesn’t keep track of this.state.list => your List only re-renders when new Item is added. And the individual Item will re-render when they are updated.

Lets say you use redux.

Your code will become something like this:

// Parent.js
class Parent extends React.Component {
  render() {        
    return <List />;
  }
}

// List.js
class List extends React.Component {
  render() {        
    var list = this.props.list.map(item => {
      return <Item key={item.key} uniqueKey={item.key} />;
    });
    return <div>{list}</div>;
  }
}

const mapStateToProps = (state) => ({
  list: getList(state)
});

export default connect(mapStateToProps)(List);
 

// Item.js
class Item extends React.Component {
  shouldComponentUpdate() {
  }
  render() {
  }
}

const mapStateToProps = (state, ownProps) => ({
  item: getItemByKey(ownProps.uniqueKey)
});

export default connect(mapStateToProps)(Item);

Of course, you have to implement the reducer and the two selectors getList and getItemByKey.

With this, you List re-render will be trigger if new elements added, or if you change item.key (which you shouldn’t)

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