在 Set() 对象上反应 JSX 循环

Question

I want to use Set object to store unique values. but by default we can't use Set.map() to make a loop on Set values in React and JSX.

But with this trick I can store Set into states and make a loop on that :

 <ul> { Array.from(this.state.mySet).map((item, index) => ( <li key={index}>{item}</li> )) } </ul>

So, Is the above trick correct and best practice to handle this issue ?

In terms of performance and concepts ...

Thanks

Answer 1

This is fine but react identifies state changes only if the state property was replaced, and not mutated/shallow compare. You'll have to use the old Set to create a new Set and then apply changes to it. That way you won't have to force update the state.

export default class Test extends React.Component {
  constructor(props) {
    super(props);

    this.state = {
      mySet: new Set()
    }

    this.add = this.add.bind(this);
  }

  add(item) {
    this.setState(({ mySet }) => ({
      mySet: new Set(mySet).add(item)
    }));
  }


  /*
  .
  .
  . Other code
  . 
  . */
}

Hope this helps !