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HTMLTextAreaElement - Web APIs 编辑

The HTMLTextAreaElement interface provides special properties and methods for manipulating the layout and presentation of <textarea> elements.

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  a:hover text { fill: #0095DD; pointer-events: all;}

Properties

`accessKey`	`string:` Returns / Sets the element's `accesskey` attribute.
`autocapitalize`	`string:` Returns / Sets the element's capitalization behavior for user input. Valid values are: `none`, `off`, `characters`, `words`, `sentences`.
`autocomplete`
`autofocus`	`boolean:` Returns / Sets the element's `autofocus` attribute, indicating that the control should have input focus when the page loads
`cols`	`unsigned long:` Returns / Sets the element's `cols` attribute, indicating the visible width of the text area.
`defaultValue`	`string:` Returns / Sets the control's default value, which behaves like the `Node.textContent` property.
`disabled`	`boolean:` Returns / Sets the element's `disabled` attribute, indicating that the control is not available for interaction.
`form` Read only	`object:` Returns a reference to the parent form element. If this element is not contained in a form element, it can be the `id` attribute of any `<form>` element in the same document or the value `null`.
`inputMode`
`maxLength`	`long:` Returns / Sets the element's `maxlength` attribute, indicating the maximum number of characters the user can enter. This constraint is evaluated only when the value changes.
`minLength`	`long:` Returns / Sets the element's `minlength` attribute, indicating the minimum number of characters the user can enter. This constraint is evaluated only when the value changes.
`name`	`string:` Returns / Sets the element's `name` attribute, containing the name of the control.
`placeholder`	`string:` Returns / Sets the element's `placeholder` attribute, containing a hint to the user about what to enter in the control.
`readOnly`	`boolean:` Returns / Sets the element's `readonly` attribute, indicating that the user cannot modify the value of the control.
`required`	`boolean:` Returns / Sets the element's `required` attribute, indicating that the user must specify a value before submitting the form.
`rows`	`unsigned long:` Returns / Sets the element's `rows` attribute, indicating the number of visible text lines for the control.
`selectionDirection`	`string:` Returns / Sets the direction in which selection occurred. This is "`forward`" if selection was performed in the start-to-end direction of the current locale, or "`backward`" for the opposite direction. This can also be "`none`" if the direction is unknown.
`selectionEnd`	`unsigned long:` Returns / Sets the index of the end of selected text. If no text is selected, contains the index of the character that follows the input cursor. On being set, the control behaves as if `setSelectionRange()` had been called with this as the second argument, and `selectionStart` as the first argument.
`selectionStart`	`unsigned long:` Returns / Sets the index of the beginning of selected text. If no text is selected, contains the index of the character that follows the input cursor. On being set, the control behaves as if `setSelectionRange()` had been called with this as the first argument, and `selectionEnd` as the second argument.
`tabIndex`	`long:` Returns / Sets the position of the element in the tabbing navigation order for the current document.
`textLength` Read only	`long:` Returns the codepoint length of the control's `value`. Same as reading `value.length`
`type` Read only	`string:` Returns the string `textarea`.
`validationMessage` Read only	`string:` Returns a localized message that describes the validation constraints that the control does not satisfy (if any). This is the empty string if the control is not a candidate for constraint validation (`willValidate` is `false`), or it satisfies its constraints.
`validity` Read only	`ValidityState object:` Returns the validity states that this element is in.
`value`	`string:` Returns / Sets the raw value contained in the control.
`willValidate` Read only	`boolean:` Returns whether the element is a candidate for constraint validation. `false` if any conditions bar it from constraint validation, including its `readOnly` or `disabled` property is `true`.
`wrap`	`string:` Returns / Sets the `wrap` HTML attribute, indicating how the control wraps text.
`HTMLTextAreaElement.labels`Read only	`NodeList`: Returns a list of label elements associated with this element.

The two properties tabIndex and accessKey are inherited from HTMLElement from HTML5 on, but were defined on HTMLTextAreaElement in DOM Level 2 HTML and earlier specifications.

Methods

`blur()`	Removes focus from the control; keystrokes will subsequently go nowhere.
`focus()`	Gives focus to the control; keystrokes will subsequently go to this element.
`select()`	Selects the contents of the control.
`setRangeText()`	Replaces a range of text in the element with new text.
`setSelectionRange()`	Selects a range of text in the element (but does not focus it).
`checkValidity()`	Returns `false` if the element is a candidate for constraint validation, and it does not satisfy its constraints. In this case, it also fires a cancelable `invalid` event at the control. It returns `true` if the control is not a candidate for constraint validation, or if it satisfies its constraints.
`reportValidity()`	This method reports the problems with the constraints on the element, if any, to the user. If there are problems, it fires a cancelable `invalid` event at the element, and returns `false`; if there are no problems, it returns `true`.
`setCustomValidity(DOMstring)`	Sets a custom validity message for the element. If this message is not the empty string, then the element is suffering from a custom validity error, and does not validate.

The two methods blur() and focus() are inherited from HTMLElement from HTML5 on, but were defined on HTMLTextAreaElement in DOM Level 2 HTML and earlier specifications.

Events

Listen to these events using addEventListener() or by assigning an event listener to the oneventname property of this interface:

input event: Fires when the value of an <input>, <select>, or <textarea> element has been changed.

Examples

Autogrowing textarea example

Make a textarea autogrow while typing:

JavaScript

function autoGrow (oField) {
  if (oField.scrollHeight > oField.clientHeight) {
    oField.style.height = oField.scrollHeight + "px";
  }
}

CSS

textarea.noscrollbars {
  overflow: hidden;
  width: 300px;
  height: 100px;
}

HTML

<form>
  <fieldset>
    <legend>Your comments</legend>
    <p><textarea class="noscrollbars" onkeyup="autoGrow(this);"></textarea></p>
    <p><input type="submit" value="Send" /></p>
  </fieldset>
</form>

Insert HTML tags example

Insert some HTML tags or smiles or any custom text in a textarea.

JavaScript

function insertMetachars(sStartTag, sEndTag) {
  var bDouble = arguments.length > 1, oMsgInput = document.myForm.myTxtArea, nSelStart = oMsgInput.selectionStart, nSelEnd = oMsgInput.selectionEnd, sOldText = oMsgInput.value;
  oMsgInput.value = sOldText.substring(0, nSelStart) + (bDouble ? sStartTag + sOldText.substring(nSelStart, nSelEnd) + sEndTag : sStartTag) + sOldText.substring(nSelEnd);
  oMsgInput.setSelectionRange(bDouble || nSelStart === nSelEnd ? nSelStart + sStartTag.length : nSelStart, (bDouble ? nSelEnd : nSelStart) + sStartTag.length);
  oMsgInput.focus();
}

CSS

CSS to decorate the internal span to behave like a link:

.intLink {
  cursor: pointer;
  text-decoration: underline;
  color: #0000ff;
}

HTML:

<form name="myForm">
<p>[&nbsp;<span class="intLink" onclick="insertMetachars('&lt;strong&gt;','&lt;\/strong&gt;');"><strong>Bold</strong></span> | <span class="intLink" onclick="insertMetachars('&lt;em&gt;','&lt;\/em&gt;');"><em>Italic</em></span> | <span class="intLink" onclick="var newURL=prompt('Enter the full URL for the link');if(newURL){insertMetachars('&lt;a href=\u0022'+newURL+'\u0022&gt;','&lt;\/a&gt;');}else{document.myForm.myTxtArea.focus();}">URL</span> | <span class="intLink" onclick="insertMetachars('\n&lt;code&gt;\n','\n&lt;\/code&gt;\n');">code</span> | <span class="intLink" onclick="insertMetachars(' :-)');">smile</span> | etc. etc.&nbsp;]</p>
<p><textarea name="myTxtArea" rows="10" cols="50">Lorem ipsum dolor sit amet, consectetur adipiscing elit. Ut facilisis, arcu vitae adipiscing placerat, nisl lectus accumsan nisi, vitae iaculis sem neque vel lectus. Praesent tristique commodo lorem quis fringilla. Sed ac tellus eros. Sed consectetur eleifend felis vitae luctus. Praesent sagittis, est eget bibendum tincidunt, ligula diam tincidunt augue, a fermentum odio velit eget mi. Phasellus mattis, elit id fringilla semper, orci magna cursus ligula, non venenatis lacus augue sit amet dui. Pellentesque lacinia odio id nisi pulvinar commodo tempus at odio. Ut consectetur eros porttitor nunc mollis ultrices. Aenean porttitor, purus sollicitudin viverra auctor, neque erat blandit sapien, sit amet tincidunt massa mi ac nibh. Proin nibh sem, bibendum ut placerat nec, cursus et lacus. Phasellus vel augue turpis. Nunc eu mauris eu leo blandit mollis interdum eget lorem. </textarea></p>
</form>

Maximum length and number of lines example

Create a textarea with a maximum number of characters per line and a maximum number of lines:

First, create a function that takes the text field and a key event as input and determines if any of the limits have been reached. If the limit has not been reached, it will return the key.

function checkRows(oField, oKeyEvent) {
  var nKey = (oKeyEvent || /* old IE */ window.event || /* check is not supported! */ { keyCode: 38 }).keyCode,

    // put here the maximum number of characters per line:
    nCols = 30,
    // put here the maximum number of lines:
    nRows = 5,

    nSelS = oField.selectionStart, nSelE = oField.selectionEnd,
    sVal = oField.value, nLen = sVal.length,

    nBackward = nSelS >= nCols ? nSelS - nCols : 0,
    nDeltaForw = sVal.substring(nBackward, nSelS).search(new RegExp("\\n(?!.{0," + String(nCols - 2) + "}\\n)")) + 1,
    nRowStart = nBackward + nDeltaForw,
    aReturns = (sVal.substring(0, nSelS) + sVal.substring(nSelE, sVal.length)).match(/\n/g),
    nRowEnd = nSelE + nRowStart + nCols - nSelS,
    sRow = sVal.substring(nRowStart, nSelS) + sVal.substring(nSelE, nRowEnd > nLen ? nLen : nRowEnd),
    bKeepCols = nKey === 13 || nLen + 1 < nCols || /\n/.test(sRow) || ((nRowStart === 0 || nDeltaForw > 0 || nKey > 0) && (sRow.length < nCols || (nKey > 0 && (nLen === nRowEnd || sVal.charAt(nRowEnd) === "\n"))));

  return (nKey !== 13 || (aReturns ? aReturns.length + 1 : 1) < nRows) && ((nKey > 32 && nKey < 41) || bKeepCols);
}

In the HTML we just need to hook our function to the `onkeypress` event and specify that our textarea does not accept pasting:

<form>
  <p>Textarea with fixed number of characters per line:<br />
    <textarea cols="50" rows="10" onkeypress="return checkRows(this, event);"
              onpaste="return false;"></textarea>
  </p>
</form>

Specifications

Specification	Status	Comment
HTML Living Standard The definition of 'HTMLTextAreaElement' in that specification.	Living Standard
HTML5 The definition of 'HTMLTextAreaElement' in that specification.	Recommendation	The attributes `tabindex` and `accesskey`, as well as the methods `blur()` and `focus()` are now defined on `HTMLElement`. The following attributes have been added: `autofocus`, `placeholder`, `dirName`, `wrap`, `maxLength`, `required`, `textLength`, `labels`, `selectionStart`, `selectionEnd`, `selectionDirection`, `validity`, `validationMessage`, and `willValidate`. The following methods have been added: `checkValidity()`, `setCustomValidity()`, and `setSelectionRange()`.
Document Object Model (DOM) Level 2 HTML Specification The definition of 'HTMLTextAreaElement' in that specification.	Obsolete	The property `defaultValue` doesn't contain the initial value of the `value` attribute, but the initial value of the content of the `<textarea>`.
Document Object Model (DOM) Level 1 Specification The definition of 'HTMLTextAreaElement' in that specification.	Obsolete	Initial definition