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@material/mwc-textarea

<mwc-textarea>

IMPORTANT: The Material Web Components are a work in progress and subject to major changes until 1.0 release.

Text areas let users enter and edit text.

Material Design Guidelines: text areas

Demo

Installation

npm install @material/mwc-textarea

NOTE: The Material Web Components are distributed as ES2017 JavaScript Modules, and use the Custom Elements API. They are compatible with all modern browsers including Chrome, Firefox, Safari, Edge, and IE11, but an additional tooling step is required to resolve bare module specifiers, as well as transpilation and polyfills for IE11. See here for detailed instructions.

Example usage

Standard

<mwc-textarea label="My Textarea"></mwc-textarea>

<script type="module">
  import '@material/mwc-textarea/mwc-textarea.js';
</script>

Helper Text

<mwc-textarea label="My Textarea" helper="Helper Text"></mwc-textarea>

Primary Color

<style>
  mwc-textarea {
    --mdc-theme-primary: green;
  }
</style>

<mwc-textarea
    label="My Textarea"
    required>
</mwc-textarea>

Variants

Outlined

<mwc-textarea
    outlined
    label="My Textarea">
</mwc-textarea>

Shaped

<style>
  mwc-textarea.rounded {
    --mdc-shape-small: 28px;
  }
</style>

<mwc-textarea
    class="rounded"
    label="My Textarea"
    outlined>
</mwc-textarea>

API

Properties/Attributes

Name	Type	Description
rows	number	Sets number of visible text lines.
cols	number	Sets the visible width of the textarea.
value	string	The input control's value.
type	TextFieldType*	A string specifying the type of control to render.
label	string	Sets floating label value.
placeholder	string	Sets disappearing input placeholder.
icon	string	Leading icon to display in input. See mwc-icon.
iconTrailing	string	Trailing icon to display in input. See mwc-icon.
disabled	boolean	Whether or not the input should be disabled.
charCounter	boolean|TextAreaCharCounter**	Note: requires maxLength to be set. Display character counter with max length. Textareas may display an "external" or "internal" charCounter. When true, textareas display an external character counter by default.
outlined	boolean	Whether or not to show the material outlined variant.
helper	string	Helper text to display below the input. Display default only when focused.
helperPersistent	boolean	Always show the helper text despite focus.
required	boolean	Displays error state if value is empty and input is blurred.
maxLength	number	Maximum length input to accept.
validationMessage	string	Message to show in the error color when the textarea is invalid. (Helper text will not be visible)
validity	ValidityState (readonly)	The ValidityState of the textfield.
willValidate	boolean (readonly)	HTMLInputElement.prototype.willValidate
validityTransform	ValidityTransform***|null	Callback called before each validation check. See the validation section for more details.
validateOnInitialRender	boolean	Runs validation check on initial render.
name	string	Sets the name attribute on the internal textarea.***

* TextFieldType is exported by mwc-textarea and mwc-textarea-base.

type TextFieldType = 'text'|'search'|'tel'|'url'|'email'|'password'|
    'date'|'month'|'week'|'time'|'datetime-local'|'number'|'color';

** TextAreaCharCounter is exported by mwc-textarea.

type TextAreaCharCounter = 'external'|'internal';

\*\*\* `ValidityTransform` is not exported. See the [validation section](#Validation) for more details.
```ts
type ValidityTransform = (value: string, nativeValidity: ValidityState) => Partial<ValidityState>

*** The name property should only be used for browser autofill as webcomponent form participation does not currently consider the name attribute. See #289.

Methods

Name	Description
checkValidity() => boolean	Returns true if the textarea passes validity checks. Returns false and fires an invalid event on the textarea otherwise.
reportValidity() => boolean	Runs checkValidity() method, and if it returns false, then it reports to the user that the input is invalid.
setCustomValidity(message:string) => void	Sets a custom validity message (also overwrites validationMessage). If this message is not the empty string, then the element is suffering from a custom validity error and does not validate.
layout() => Promise<void>	Re-calculate layout. If a textarea is styled with display:none before it is first rendered, and it has a label that is floating, then you must call layout() the first time you remove display:none, or else the notch surrounding the label will not render correctly.

CSS Custom Properties

Inherits CSS Custom properties from:

• mwc-ripple
• mwc-notched-outline.
• mwc-icon

Name	Default	Description
--mdc-text-area-filled-border-radius	4px 4px 0 0	Border radius of the standard / filled textarea's background filling.
--mdc-text-area-outlined-idle-border-color	rgba(0, 0, 0, 0.38)	Color of the outlined textarea's outline when idle.
--mdc-text-area-outlined-hover-border-color	rgba(0, 0, 0, 0.87)	Color of the outlined textarea's outline when hovering.
--mdc-text-area-outlined-disabled-border-color	rgba(0, 0, 0, 0.06)	Color of the outlined textarea's outline when disabled.

Global Custom Properties

This component exposes the following global theming custom properties.

Name	Description
--mdc-theme-primary	Color when active of the underline ripple, the outline, and the caret.
--mdc-theme-error	Color when errored of the underline, the outline, the caret, and the icons.
--mdc-typography-subtitle1-<PROPERTY>	Styles the typography of the texarea, excluding line-height.

Validation

<mwc-textarea> follows the basic <input> constraint validation model. It exposes:

• required
• maxLength
• validity
• willValidate
• checkValidity()
• reportValidity()
• setCustomValidity(message)

Additionally, it implements more features such as:

• validationMessage
• validateOnInitialRender
• and validityTransform

By default, <mwc-textarea> will report validation on blur.

Custom validation logic

The validityTransform property is a function that can be set on <mwc-textarea> to implement custom validation logic that transforms the ValidityState of the input control. The type of a ValidityTransform is the following:

(value: string, nativeValidity: ValidityState) => Partial<ValidityState>

Where value is the new value in the textarea to be validated and nativeValidity is an interface of ValidityState of the native input control. For example:

<mwc-textarea
    id="my-textarea"
    maxlength="5"
    value="doggos">
</mwc-textarea>
<script>
  const textarea = document.querySelector('#my-textarea');
  textarea.validityTransform = (newValue, nativeValidity) => {
    if (!nativeValidity.valid) {
      if (nativeValidity.tooLong) {
        const hasDog = newValue.includes('dog');
        // changes to make to the nativeValidity
        return {
          valid: hasDog,
          tooLong: !hasDog;
        };
      } else {
        // no changes
        return {};
      }
    } else {
      const isValid = someExpensiveOperation(newValue);
      // changes to make to the native validity
      return {
        valid: isValid,
        // or whatever type of ValidityState prop you would like to set (if any)
        customError: !isValid,
      };
    }
  }
</script>

In this example we first check the native validity which is invalid due to the maxlength (the value is doggos which is a string longer than 5). The value includes dog, thus we make it valid and undo the tooLong error in the ValidityState by returning a Partial<ValidityState> that indicates what to change in the initial validity.

In this example, we also skip an expensive validity check by short-circuiting the validation by checking the native validation.

Note: the UI will only update as valid / invalid by checking the valid property of the transformed ValidityState.

Additional references

• MDC Web textfields