Question 74250 in Reactjs Question posted in
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Pushing form values to an array. (React) – Reactjs

I’m having some trouble pushing the values from my form to an array that I’m mapping on screen.

const ForumTopic = [
  {
    title: "First Post",
    messages: "test",
    author: "Dagger",
    count: 1,
    date: "02/16",
  },
];

const [topic, setTopic] = useState(ForumTopic);

Storing ForumTopic in state so I can add entries and display on screen after I click the submit button below.

  const addTopic = (e) => {
    e.preventDefault();
    setTopic([...topic, e.target.value]);
  };

  <form onSubmit={addTopic}>
          Create a topic title
          <label htmlFor="title">
            <input id="title"></input>
          </label>
          Write your message
          <label htmlFor="message">
            <textarea id="message"></textarea>
          </label>
          <label htmlFor="author">
            <input id="author" defaultValue="Dagger" hidden></input>
          </label>
          <label htmlFor="count">
            <input id="count" defaultValue="1" hidden></input>
          </label>
          <label htmlFor="date">
            <input id="date" defaultValue="02/16/2023" hidden></input>
          </label>
          <button type="submit">
            Post New Message
          </button>
        </form>

That’s my code and form. The code is meant to push the values from each label in the form to create a new object inside the topic array. I want everything stored in a new object with the id of each label to match the names of each object (title, author, date, etc) but for some reason all I’m getting are undefined errors.

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2

Answers


  1. 0

    The problem is that on your addTopic function:
    e.target.value are always undefined

    to access the data you have to do:

    const addTopic = (e) => {
    e.preventDefault()

    const myData = {
        title: e.target.title.value,
        message: e.target.message.value
    }
    
    setTopic(prev => [...prev, myData])        

}
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  2. 0

    A simple way to do it is like this.

    You need to obtain the value you are getting with an onChange in the input.

    LINK to the example: https://stackblitz.com/edit/react-8r9f8l?file=src%2FApp.js

    import React, { useState } from 'react';

const ForumTopic = [
  {
    title: 'First Post',
    messages: 'test',
    author: 'Dagger',
    count: 1,
    date: '02/16',
  },
];

export default function App() {
  const [topic, setTopic] = useState(ForumTopic);
  const [inputObj, setInputObj] = useState({
    title: '',
    messages: '',
    author: 'Dagger',
    count: 1,
    date: '02/16',
  });

  const handleChange = (event) => {
    setInputObj((curr) => ({
      ...curr,
      [event.target.name]: event.target.value,
    }));
  };

  const addTopic = (e) => {
    e.preventDefault();
    setTopic([...topic, inputObj]);
  };

  return (
    <>
      <form onSubmit={addTopic}>
        <label htmlFor="title">
          Create a topic title
          <input
            id="title"
            name="title"
            value={inputObj.title}
            onChange={handleChange}
          ></input>
        </label>
        <label htmlFor="message">
          Write your message
          <textarea
            id="message"
            name="messages"
            value={inputObj.messages}
            onChange={handleChange}
          ></textarea>
        </label>
        <label htmlFor="author">
          <input id="author" name="author" defaultValue="Dagger" hidden></input>
        </label>
        <label htmlFor="count">
          <input id="count" name="count" defaultValue="1" hidden></input>
        </label>
        <label htmlFor="date">
          <input id="date" name="date" defaultValue="02/16/2023" hidden></input>
        </label>
        <button type="submit">Post New Message</button>
      </form>
      {topic.map((item) => {
        return (
          <>
            <p>{item.title}</p>
            <p>{item.messages}</p>
            <p>{item.author}</p>
            <p>{item.count}</p>
            <p>{item.date}</p>
            <span>------------</span>
          </>
        );
      })}
    </>
  );
}
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