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HTML form

Input fields on a Web page

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Description

Forms are enclosed in the HTML <form> element. This HTML element specifies the communication endpoint the data entered into the form should be submitted to, and the method of submitting the data, GET or POST.

Elements

Forms can be made up of standard graphical user interface elements:

  • <button> — a button that can be tied to action such as submitting the form, resetting the form or executing a JavaScript function.
  • <input> — a element for user input. The element varies by the value of its type attribute.
  • <textarea> — much like the <text> input field except a <textarea> allows for multiple rows of data to be shown and entered
  • <select> — a drop-down list that displays a list of items a user can select from

The input element can have the following types:

  • text — a simple text box that allows input of a single line of text.
  • email - a type of <text> that requires a partially validated email address
  • number - a type of <text> that requires a number
  • password — similar to <text>, it is used for security purposes, in which the characters typed in are invisible or replaced by symbols such as *
  • tel — a telephone number
  • radio — a radio button
  • file — a file select control for uploading a file
  • reset — a reset button that, when activated, tells the browser to restore the values of the current form, to their initial values.
  • submit — a button that tells the browser to take action on the form (typically to send it to a server)

The sample image on the right shows most of these elements:

  • a text box asking for your name
  • a pair of radio buttons asking you to choose between gender values
  • a select box giving you a list of eye colors to choose from
  • a pair of check boxes to click on if they apply to you
  • a text area to describe your athletic ability
  • a submit button to send current form values to the server

These basic elements provide the most common graphical user interface (GUI) elements, but not all. For example, there are no equivalents to a tree view or grid view.

A grid view, however, can be mimicked by using a standard HTML table with each cell containing a text input element. A tree view could also be mimicked through nested tables or, more semantically appropriately, nested lists. In both cases, a server-side process is responsible for processing the information, while JavaScript handles the user-interaction. Implementations of these interface elements are available through JavaScript libraries such as jQuery.

HTML 4 introduced the <label> tag, which is intended to represent a caption in a user interface, and can be associated with a specific form control by specifying the id attribute of the control in the label tag's for attribute. This allows labels to stay with their elements when a window is resized and to allow more desktop-like functionality (e.g. clicking a radio button or checkbox's label will activate the associated input element).

HTML 5 introduces a number of input types that can be represented by other interface elements. Some are based upon text input fields and are intended to input and validate specific common data. These include email to enter email addresses, tel for telephone numbers, number for numeric values. There are additional attributes to specify required fields, fields that should have keyboard focus when the web page containing the form is loaded, and placeholder text that is displayed within the field but is not user input (such as the 'Search' text displayed in many search input fields before a search term is entered). These tasks used to be handled with JavaScript, but had become so common that support for them was added to the standard. The date input type displays a calendar from which the user can select a date or date range. And the color input type can be represented as an input text simply checking the value entered is a correct hexadecimal representation of a color, according to the specification, or a color picker widget (the latter being the solution used in most browsers which support this attribute).

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