I'm trying to complete my first todo-app in next js 13 using typescript but whenever I try to add a task in my task list I get the error given below
Unhandled Runtime Error
TypeError: tasks.map is not a function.

I have prvided the code from page.tsx file below:

"use client"
import "./globals.css";
import { Button, Flex, ListItem, UnorderedList, Text, Input } from "@chakra-ui/react";
import { useState } from "react";
export default function Home() {
  const [tasks, setTasks] = useState(["1", "2", "3"]);
  const [Item, setItem] = useState("");
function removeItem(taskName){
  setTasks(
    tasks.filter((task) => {
      return task!= taskName;
  })
  );
}
function AddItem(taskName){
  if(Item!="" && !tasks.includes(Item));
  let temp=tasks
  temp.push(Item);
  setTasks(Item);
  setItem("");
}
  return (
    <Flex
      justifyContent="center"
      alignItems="center"
      width="100%"
      height="100%"
      flexDirection="column"
    >
      <UnorderedList>
        {tasks.map((task) => {
          return (
            <ListItem key={task.index}>
              {task}
              <Button
                ml={10}
                onClick={() => {
                  removeItem(task); 
                }}>
                Remove Item
              </Button>
            </ListItem>
          )
        })}
      </UnorderedList>
      <Input
        placeContent="item name"
        value={Item}
        onChange={(e) => {
          setItem(e.target.value);
        }}>
      </Input>
<Button onClick={AddItem}>
  Add Item
</Button>
    </Flex>
  )
}

CodePudding user response：

Update the function AddItem to recreate the tasks array using the spread operator instead:

function AddItem(taskName){
  if(Item!="" && !tasks.includes(Item));
  let temp=[...tasks]
  temp.push(Item);
  setTasks(Item);
  setItem("");
}

CodePudding user response：

You are setting tasks to an individual item here:

setTasks(Item);

I imagine you want temp here instead of Item:

setTasks(temp);

If item is anything other than an array the map function will not be valid and throw an error.

Also, in your AddItem function, you're mutating state and your if statment isn't actually wrapping anything so I would just rewrite the whole thing to the following:

function AddItem(taskName) {
  if (Item != '' && !tasks.includes(Item)) {
    setTasks([...tasks, Item]);
    setItem('');
  }
}

I'm assuming you have plans for taskName.

Hope this helps.