Search code examples
javascriptreactjsuse-state

How to update state with usestate in an array of objects?


I'm having some trouble with the React useState hook. I have a todolist with a checkbox button and I want to update the 'done' property to 'true' that has the same id as the id of the 'clicked' checkbox button. If I console.log my 'toggleDone' function it returns the right id. But I have no idea how I can update the right property.

The current state:

const App = () => {

  const [state, setState] = useState({
    todos: 
    [
        {
          id: 1,
          title: 'take out trash',
          done: false
        },
        {
          id: 2,
          title: 'wife to dinner',
          done: false
        },
        {
          id: 3,
          title: 'make react app',
          done: false
        },
    ]
  })

  const toggleDone = (id) => {
    console.log(id);
}

  return (
    <div className="App">
        <Todos todos={state.todos} toggleDone={toggleDone}/>
    </div>
  );
}

The updated state I want:

const App = () => {

  const [state, setState] = useState({
    todos: 
    [
        {
          id: 1,
          title: 'take out trash',
          done: false
        },
        {
          id: 2,
          title: 'wife to dinner',
          done: false
        },
        {
          id: 3,
          title: 'make react app',
          done: true // if I checked this checkbox.
        },
    ]
  })

Solution

  • You can safely use javascript's array map functionality since that will not modify existing state, which react does not like, and it returns a new array. The process is to loop over the state's array and find the correct id. Update the done boolean. Then set state with the updated list.

    const toggleDone = (id) => {
      console.log(id);
    
      // loop over the todos list and find the provided id.
      let updatedList = state.todos.map(item => 
        {
          if (item.id == id){
            return {...item, done: !item.done}; //gets everything that was already in item, and updates "done"
          }
          return item; // else return unmodified item 
        });
    
      setState({todos: updatedList}); // set state to new object with updated list
    }
    

    Edit: updated the code to toggle item.done instead of setting it to true.