Selaimen sisäänrakennettu <textarea>-komponentti mahdollistaa monirivisen tekstisyötteen renderöimisen.

<textarea />

Viite

<textarea>

Näyttääksesi tekstikentän, renderöi selaimen sisäänrakennettu <textarea>-komponentti.

<textarea name="postContent" />

Näe lisää esimerkkejä alla.

Propsit

<textarea> tukee kaikkia yleisten elementtien propseja.

Voit tehdä tekstikentästä kontrolloidun välittämällä value propsin:

  • value: Merkkijono. Kontrolloi tekstikentän tekstiä..

Kun välität value-arvon, sinun täytyy myös välittää onChange-käsittelijä, joka päivittää välitetyn arvon.

Jos <textarea> on kontrolloimaton, voit välittää defaultValue-propsin sen sijaan:

  • defaultValue: Merkkijono. Määrittelee oletusarvon tekstikentälle.

Nämä <textarea>-propsit ovat relevantteja sekä kontrolloimattomille että kontrolloiduille tekstikentille:

  • autoComplete: Joko 'on' tai 'off'. Määrittelee automaattisen täydentämisen käyttäytymistä.
  • autoFocus: Totuusarvo. Jos true, React kodhistaa elementtiin mountatessa.
  • children: <textarea> ei hyväksy lapsia. Oletusarvon asettamiseksi, käytä defaultValue.
  • cols: Numero. Määrittää oletusleveyden keskimääräisinä merkkileveyksinä. Oletuksena arvoltaan 20.
  • disabled: Totuusarvo. Jos true, kenttä ei ole interaktiivinen ja näkyy himmennettynä.
  • form: Merkkijono. Määrittää <form> lomakkeen id :n johon tämä kenttä kuuluu. Jos jätetty pois, se on lähin ylätason lomake.
  • maxLength: Numero. Määrittää tekstin enimmäispituuden.
  • minLength: Numero. Määrittää tekstin vähimmäispituuden.
  • name: Merkkijono. Määrittää nimen tälle kentälle, joka lähetetään lomakkeessa.
  • onChange: Event käsittelijäfunktio. Vaaditaan ohjattuihin tekstikenttiin. Suoritetaan heti kun käyttäjä muuttaa kentän arvoa (esimerkiksi, suoritetaan jokaisella näppäinpainalluksella). Käyttäytyy kuten selaimen input tapahtuma.
  • onChangeCapture: Versio onChange:sta, joka suoritetaan capture phase.
  • onInput: Event käsittelijäfunktio. function. Fires immediately when the value is changed by the user. For historical reasons, in React it is idiomatic to use onChange instead which works similarly.
  • onInputCapture: Versio onInput:sta joka suoritetaan nappausvaiheessa.
  • onInvalid: Event käsittelijäfunktio. Fires if an input fails validation on form submit. Unlike the built-in invalid event, the React onInvalid event bubbles.
  • onInvalidCapture: Versio onInvalid:sta joka suoritetaan nappausvaiheessa.
  • onSelect: Event käsittelijäfunktio. Fires after the selection inside the <textarea> changes. React extends the onSelect event to also fire for empty selection and on edits (which may affect the selection).
  • onSelectCapture: Versio onSelect:sta joka suoritetaan nappausvaiheessa.
  • placeholder: Merkkijono. Displayed in a dimmed color when the text area value is empty.
  • readOnly: Totuusarvo. If true, the text area is not editable by the user.
  • required: Totuusarvo. If true, the value must be provided for the form to submit.
  • rows: Numero. Määrittää oletuskorkeuden keskimääräisinä merkkikorkeuksina. Defaults to 2.
  • wrap: Joko 'hard', 'soft', tai 'off'. Määrittää miten tekstin tulisi rivittyä lomaketta lähettäessä.

Rajoitukset

  • Passing children like <textarea>something</textarea> is not allowed. Use defaultValue for initial content.
  • If a text area receives a string value prop, it will be treated as controlled.
  • A text area can’t be both controlled and uncontrolled at the same time.
  • A text area cannot switch between being controlled or uncontrolled over its lifetime.
  • Every controlled text area needs an onChange event handler that synchronously updates its backing value.

Käyttö

Displaying a text area

Render <textarea> to display a text area. You can specify its default size with the rows and cols attributes, but by default the user will be able to resize it. To disable resizing, you can specify resize: none in the CSS.

export default function NewPost() {
  return (
    <label>
      Write your post:
      <textarea name="postContent" rows={4} cols={40} />
    </label>
  );
}

Providing a label for a text area

Typically, you will place every <textarea> inside a <label> tag. This tells the browser that this label is associated with that text area. When the user clicks the label, the browser will focus the text area. It’s also essential for accessibility: a screen reader will announce the label caption when the user focuses the text area.

If you can’t nest <textarea> into a <label>, associate them by passing the same ID to <textarea id> and <label htmlFor>. To avoid conflicts between instances of one component, generate such an ID with useId.

import { useId } from 'react';

export default function Form() {
  const postTextAreaId = useId();
  return (
    <>
      <label htmlFor={postTextAreaId}>
        Write your post:
      </label>
      <textarea
        id={postTextAreaId}
        name="postContent"
        rows={4}
        cols={40}
      />
    </>
  );
}

Providing an initial value for a text area

You can optionally specify the initial value for the text area. Pass it as the defaultValue string.

export default function EditPost() {
  return (
    <label>
      Edit your post:
      <textarea
        name="postContent"
        defaultValue="I really enjoyed biking yesterday!"
        rows={4}
        cols={40}
      />
    </label>
  );
}

Sudenkuoppa

Unlike in HTML, passing initial text like <textarea>Some content</textarea> is not supported.

Reading the text area value when submitting a form

Add a <form> around your textarea with a <button type="submit"> inside. It will call your <form onSubmit> event handler. By default, the browser will send the form data to the current URL and refresh the page. You can override that behavior by calling e.preventDefault(). Read the form data with new FormData(e.target).

export default function EditPost() {
  function handleSubmit(e) {
    // Prevent the browser from reloading the page
    e.preventDefault();

    // Read the form data
    const form = e.target;
    const formData = new FormData(form);

    // You can pass formData as a fetch body directly:
    fetch('/some-api', { method: form.method, body: formData });

    // Or you can work with it as a plain object:
    const formJson = Object.fromEntries(formData.entries());
    console.log(formJson);
  }

  return (
    <form method="post" onSubmit={handleSubmit}>
      <label>
        Post title: <input name="postTitle" defaultValue="Biking" />
      </label>
      <label>
        Edit your post:
        <textarea
          name="postContent"
          defaultValue="I really enjoyed biking yesterday!"
          rows={4}
          cols={40}
        />
      </label>
      <hr />
      <button type="reset">Reset edits</button>
      <button type="submit">Save post</button>
    </form>
  );
}

Huomaa

Give a name to your <textarea>, for example <textarea name="postContent" />. The name you specified will be used as a key in the form data, for example { postContent: "Your post" }.

Sudenkuoppa

By default, any <button> inside a <form> will submit it. This can be surprising! If you have your own custom Button React component, consider returning <button type="button"> instead of <button>. Then, to be explicit, use <button type="submit"> for buttons that are supposed to submit the form.

Controlling a text area with a state variable

A text area like <textarea /> is uncontrolled. Even if you pass an initial value like <textarea defaultValue="Initial text" />, your JSX only specifies the initial value, not the value right now.

To render a controlled text area, pass the value prop to it. React will force the text area to always have the value you passed. Typically, you will control a text area by declaring a state variable:

function NewPost() {
  const [postContent, setPostContent] = useState(''); // Declare a state variable...
  // ...
  return (
    <textarea
      value={postContent} // ...force the input's value to match the state variable...
      onChange={e => setPostContent(e.target.value)} // ... and update the state variable on any edits!
    />
  );
}

This is useful if you want to re-render some part of the UI in response to every keystroke.

import { useState } from 'react';
import MarkdownPreview from './MarkdownPreview.js';

export default function MarkdownEditor() {
  const [postContent, setPostContent] = useState('_Hello,_ **Markdown**!');
  return (
    <>
      <label>
        Enter some markdown:
        <textarea
          value={postContent}
          onChange={e => setPostContent(e.target.value)}
        />
      </label>
      <hr />
      <MarkdownPreview markdown={postContent} />
    </>
  );
}

Sudenkuoppa

If you pass value without onChange, it will be impossible to type into the text area. When you control an text area by passing some value to it, you force it to always have the value you passed. So if you pass a state variable as a value but forget to update that state variable synchronously during the onChange event handler, React will revert the text area after every keystroke back to the value that you specified.

Vianmääritys

My text area doesn’t update when I type into it

If you render a text area with value but no onChange, you will see an error in the console:

// 🔴 Bug: controlled text area with no onChange handler
<textarea value={something} />
Konsoli
You provided a value prop to a form field without an onChange handler. This will render a read-only field. If the field should be mutable use defaultValue. Otherwise, set either onChange or readOnly.

As the error message suggests, if you only wanted to specify the initial value, pass defaultValue instead:

// ✅ Good: uncontrolled text area with an initial value
<textarea defaultValue={something} />

If you want to control this text area with a state variable, specify an onChange handler:

// ✅ Good: controlled text area with onChange
<textarea value={something} onChange={e => setSomething(e.target.value)} />

If the value is intentionally read-only, add a readOnly prop to suppress the error:

// ✅ Good: readonly controlled text area without on change
<textarea value={something} readOnly={true} />

My text area caret jumps to the beginning on every keystroke

If you control a text area, you must update its state variable to the text area’s value from the DOM during onChange.

You can’t update it to something other than e.target.value:

function handleChange(e) {
  // 🔴 Bug: updating an input to something other than e.target.value
  setFirstName(e.target.value.toUpperCase());
}

You also can’t update it asynchronously:

function handleChange(e) {
  // 🔴 Bug: updating an input asynchronously
  setTimeout(() => {
    setFirstName(e.target.value);
  }, 100);
}

To fix your code, update it synchronously to e.target.value:

function handleChange(e) {
  // ✅ Updating a controlled input to e.target.value synchronously
  setFirstName(e.target.value);
}

If this doesn’t fix the problem, it’s possible that the text area gets removed and re-added from the DOM on every keystroke. This can happen if you’re accidentally resetting state on every re-render. For example, this can happen if the text area or one of its parents always receives a different key attribute, or if you nest component definitions (which is not allowed in React and causes the “inner” component to remount on every render).

I’m getting an error: “A component is changing an uncontrolled input to be controlled”

If you provide a value to the component, it must remain a string throughout its lifetime.

You cannot pass value={undefined} first and later pass value="some string" because React won’t know whether you want the component to be uncontrolled or controlled. A controlled component should always receive a string value, not null or undefined.

If your value is coming from an API or a state variable, it might be initialized to null or undefined. In that case, either set it to an empty string ('') initially, or pass value={someValue ?? ''} to ensure value is a string.

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