React list elements does not render

Question

Here I am trying to render my tasks' titles in a list. But for some reason they don't render. Here is the MyTasks component:

const MyTasks = (props) => {
  const tasks = [...props.tasks];
  console.log(props.tasks, "props.tasks");
  console.log(tasks, "tasks");
  console.log(tasks[0], "tasks[0]");
  return (
    <ListGroup className="mx-2 mt-4">
      {tasks.map((task) => {
        return <ListGroup.Item key={task.id}>{task.title}</ListGroup.Item>;
      })}
    </ListGroup>
  );
};

export default MyTasks;

I tried console.log inside the component but for some reason I can't access the array elements but I can view the props.tasks array.

In my TaskLists component I am rendering the MyTasks component.

TaskLists component is using a useState hook for updating the tasks prop value of the MyTasks component but during the child component re-render I am not able to access the elements in the props.tasks array.

const TaskList = () => {
  const [tasks, setTasks] = useState([]);
  const getTasks = () => {
  //code to get tasks data from data base
  setTasks(taskList);
};
  return (
    <ListGroup className="mx-2 mt-4">
      <MyTasks tasks={tasks} />
    </ListGroup>
  );
};

Here is my console.log screenshot, I cant access the array elements for some reason.

`props.tasks.indexOf(i).id` probably throws an error `cannot access id of undefined`. Replace it with `element.id` — Martin, Jun 09 '23 at 11:09
@Martin as you can see from the tagged picture`props.tasks` is an array and has index of 1 and 2 — ash543210, Jun 09 '23 at 11:11
Instead of props.tasks, you have to use props.tasks[0] in the map. — Maulik Patel, Jun 09 '23 at 11:12
@Martin tried replacing it with `element.id` it is still the same — ash543210, Jun 09 '23 at 11:13
@MaulikPatel I have used the `forEach` loop on the `props.tasks` array that has tasks objects and tried to push them into `let list` array — ash543210, Jun 09 '23 at 11:25
Are you sure you are using the `ListGroup.Item` component properly? Where does that component come from? What happens if you just replace it with a `div`? [Here is your code](https://codepen.io/denk0403/pen/MWzYPQp?editors=0010) working without `ListGroup.Item`. — Dennis Kats, Jun 09 '23 at 11:26
Please add a [mre]. And use `map()` no need for that forEach and `list` array. — 0stone0, Jun 09 '23 at 11:29
@DennisKats I have tried replacing `ListGroup.Item ` with just `li` still it doesn't work. — ash543210, Jun 09 '23 at 11:39
@ash543210 It seems like then there is some other code that you're not showing us that is the source of your issue. As mentioned above, please try to include a [minimal reproducible example](https://stackoverflow.com/help/minimal-reproducible-example) so that we can better assist you. — Dennis Kats, Jun 09 '23 at 11:44
@DennisKats in the above code when i tried logging the`element` object, there is nothing in the`console` — ash543210, Jun 09 '23 at 11:51
@ash543210 Do you mean `console.log(element)` prints `undefined`? Can you try logging `console.log(JSON.stringify(props.tasks))`? — Dennis Kats, Jun 09 '23 at 11:58
@DennisKats no what I mean is it doesn't log anything at all. everything inside the`forEach` loop. — ash543210, Jun 09 '23 at 12:00
It sounds like initially and at render time `props.tasks` is an empty array. That's why `console.log(element)` isn't printing anything, because the `forEach` loop never runs on an empty array. However, by the time you inspect the value in the console, the `props.tasks` array has been mutated by reference with new data. Are you fetching tasks asynchronously? Again, this would be easier to debug if you edited your question to include how `` is used, and how `tasks` is defined. — Dennis Kats, Jun 09 '23 at 12:06

score 0 · Answer 1 · answered Jun 09 '23 at 11:13

0

props.tasks.indexOf(i) is attempting to return the index of the element i, however i itself is the index! Instead, try using element.id as suggested in the comment above.

answered Jun 09 '23 at 11:13

Stitt

406
2
8

I just realised it changed the code but nothing changed – ash543210 Jun 09 '23 at 11:20

score 0 · Answer 2 · answered Jun 09 '23 at 11:16

0

Can you please try to console.log inside the foreach, so verify first the values you are getting inside the loop. If you can get then it should print, otherwise you will get to know where is the issue.

answered Jun 09 '23 at 11:16

sayan0020

36
1
3
9

I just did and it's the same as from the first picture – ash543210 Jun 09 '23 at 11:18
can you please paste the output of props, as you shared with us as screenshot. It is hard to replicate from the screenshot. I like to try in code, so I can help you better – sayan0020 Jun 09 '23 at 11:51
I have posted the screenshot for both `props` and `props.tasks` – ash543210 Jun 09 '23 at 12:05
As @dennis-kats says if you are getting the value from a asynchronous call, then use asyn await so it would wait for the response, then do the operation. – sayan0020 Jun 09 '23 at 12:13
No, i am getting the value from a component state value using `useState()` – ash543210 Jun 09 '23 at 12:18
@ash543210 I think you are getting array-like object instead on array. I have faced an issue in array-like. Please check the below link, it may help https://stackoverflow.com/questions/29707568/javascript-difference-between-array-and-array-like-object – sayan0020 Jun 12 '23 at 07:05

score 0 · Answer 3 · answered Jun 09 '23 at 11:43

The code you provided seems to be a React component called MyTasks. It appears that you're trying to render a list of task titles using the props.tasks array. However, you mentioned that the task titles are not rendering.

Here are a few suggestions to troubleshoot the issue:

Check if props.tasks is correctly passed to the component: Make sure you're passing the tasks prop to the MyTasks component correctly from its parent component.
Verify the data structure of props.tasks: Ensure that props.tasks is an array of objects and each object has a title property. You can use console.log to inspect the props.tasks data structure and verify if it matches your expectations.
Ensure the component is being rendered: Double-check that the MyTasks component is being rendered in the parent component's JSX code. Without rendering the component, its logic won't be executed.
Verify if the props.tasks array is empty: If the props.tasks array is empty, the forEach loop won't execute, and no list items will be added to the list array. Make sure the props.tasks array contains the necessary data.
Check for any errors in the console: Look for any error messages in the browser's console that might indicate the source of the problem.

By examining these points, you should be able to identify the issue and resolve it.

I have tried all the troubleshoot tips and yes the list renders but it's empty and also the `props.tasks` is an `array` as in the picture and also it has all the information needed to render the component — ash543210, Jun 09 '23 at 11:53

React list elements does not render

3 Answers3