HTML Form Elements

This chapter describes all HTML form elements.

The <input> Element

The most important form element is the <input> element.

The <input> element can vary in many ways, depending on the type attribute.

	All HTML input types are covered in the next chapter.

The <select> Element (Drop-Down List)

The <select> element defines a drop-down list:

The <option> elements defines the options to select.

The list will normally show the first item as selected.

You can add a selected attribute to define a predefined option.

The <textarea> Element

The <textarea> element defines a multi-line input field (a text area):

This is how the HTML code above will be displayed in a browser:

The <button> Element

The <button> element defines a clickable button:

This is how the HTML code above will be displayed in a browser:

HTML5 Form Elements

HTML5 added the following form elements:

• <datalist>
• <keygen>
• <output>

	By default, browsers do not display unknown elements. New elements will not destroy your page.

HTML5 <datalist> Element

The <datalist> element specifies a list of pre-defined options for an <input> element.

Users will see a drop-down list of pre-defined options as they input data.

The list attribute of the <input> element, must refer to the id attribute of the <datalist> element.

Example

An <input> element with pre-defined values in a <datalist>:

<form action="action_page.php">
  <input list="browsers">
  <datalist id="browsers">
    <option value="Internet Explorer">
    <option value="Firefox">
    <option value="Chrome">
    <option value="Opera">
    <option value="Safari">
  </datalist>
</form>

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HTML5 <keygen> Element

The purpose of the <keygen> element is to provide a secure way to authenticate users.

The <keygen> element specifies a key-pair generator field in a form.

When the form is submitted, two keys are generated, one private and one public.

The private key is stored locally, and the public key is sent to the server.

The public key could be used to generate a client certificate to authenticate the user in the future.

Example

A form with a keygen field:

<form action="action_page.php">
  Username: <input type="text" name="user">
  Encryption: <keygen name="security">
  <input type="submit">
</form>

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HTML5 <output> Element

The <output> element represents the result of a calculation (like one performed by a script).

Example

Perform a calculation and show the result in an <output> element:

<form action="action_page.asp"
  oninput="x.value=parseInt(a.value)+parseInt(b.value)">
  0
  <input type="range"  id="a" name="a" value="50">
  100 +
  <input type="number" id="b" name="b" value="50">
  =
  <output name="x" for="a b"></output>
  <br><br>
  <input type="submit">
</form>

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