How to concatenate multiple values in react state array

Question

I have created a todo list app I can add or remove elements in that list I am using react state for this purpose. Adding new element is perfectly working but removal isn't whenever I click on remove it just remove everything except the last item I have added I am using removeItem method to perform this functionality and I am filtering that clicked value and map rest of values in this function and I have tried to print those values in console ad well and I am getting desired output in console but those values are not getting stored in state array and I don't know why its happening:

import { useState } from 'react';
import './App.css';

let App = ()=>{

const [initial, addInitial] = useState('');
const [val, addVal] = useState([]);

  let changeHandler = (e)=>{
    addInitial(e.target.value)
  }

  let addItem =(event)=>{

      let newItem = initial;
      addVal( (prevValues) => [...prevValues, newItem]);
  }

  let removeItem = (par)=>{
 
    val.map((value, index)=>{
       if(index != par){
         addVal([ [...value] ])         
       }else{
         
       } 
    })

  }

    return(
    <div id="parent">
        <div id="container">
            <h1>To-Do List</h1>

          <div id="sub1">
            <input type="text" value={initial} onChange ={changeHandler} placeholder='Add a item' autoFocus/>
            <button id="add" onClick = {addItem}>+</button>
          </div>
          
            
          <div id="sub2">
            
            {
              val.map((name, index)=>{
                return(
                  <div id="cross" key={index}> 
                    <button className="remove" id={index} onClick = { ()=> removeItem(index)}>&#10060;</button>
                    {name}
                  </div>
                )})
            }

          </div>
        </div>
    </div>
    )
}

export default App;

Ahmad · Accepted Answer · 2022-07-20 11:21:44Z

2

I updated you removeItem function, you have to use filter instead of map, could you please try this.

  let removeItem = (par)=>{
    const filter = val.filter((_, index) => index !== par);
    addVal(filter)
  }

edited Jul 20, 2022 at 11:21

answered Jul 20, 2022 at 11:14

Ahmad

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Comments

snehal gugale · Accepted Answer · 2022-07-20 11:19:19Z

1

Instead of using map method just use filter method to filter out the removed item

let removeItem = (par)=>{
  const arr = val.filter((item,index) => index != par)
  addVal(arr)
}

answered Jul 20, 2022 at 11:19

snehal gugale

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Comments

RKataria · Accepted Answer · 2022-07-20 11:13:07Z

0

You can user array.splice to achieve your functionality:

let removeItem = (par) => {
    const temp = [...val];
    temp.splice(par, 1);
    addVal([...temp]);
};

answered Jul 20, 2022 at 11:13

RKataria

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1 Comment

Anas Over a year ago

I don't know why but I am still getting same output as earlier like I am getting just last element whenever I click on remove button :(

SCHYNS Anthony · Accepted Answer · 2022-07-20 11:16:29Z

0

Ok so it seems you are using "map" to remove item, instead you can use "filter" method.

    const removeItem = (index)=>{
    const filteredArray = val.filter((item, i) => i !== index)
    addVal([...filteredArray])
  }

The filter method remove all items that does not met the condition

answered Jul 20, 2022 at 11:16

SCHYNS Anthony

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Comments

g.p · Accepted Answer · 2022-07-20 11:22:05Z

For just fixing your code, change removeItem to this

  let removeItem = (par)=>{

    let newValues = [];
    val.forEach((v, index) => {
      if(index !== par){
       newValues.push(v)
      }
    })
   addVal(newValues)

  }

A better way to rewrite the app would be

const App = ()=>{

  const [todo, changeTodo] = useState('');
  const [todos, addTodos] = useState([]);

  const changeTodoTextHandler = (e)=>{
    changeTodo(e.target.value)
  }

  const addTodo = ()=>{
    addTodos([...todos, todo])
    changeTodo('')
  }

  const removeTodo = (todoToDelete)=>{
    const updatedTodos = todos.reduce((acc, current) => {
      if(current !== todoToDelete) {
        return [...acc, current]
      }
      return [...acc]
    }, [])
    addTodos(updatedTodos)
  }

  return(
      <div id="parent">
        <div id="container">
          <h1>To-Do List</h1>
          <div id="sub1">
            <input type="text" value={todo} onChange ={changeTodoTextHandler} placeholder='Add a item' autoFocus/>
            <button id="add" onClick = {addTodo}>+</button>
          </div>
          <div id="sub2">
            {
              todos.map((todoName)=>{
                return(
                    <div id="cross" key={todoName}>
                      <button className="remove" onClick = { ()=> removeTodo(todoName)}>&#10060;</button>
                      {todoName}
                    </div>
                )})
            }
          </div>
        </div>
      </div>
  )
}

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