项目介绍

Forms and Input Elements of HTML

The George Washington University

Computer Science 1023

Professor Brenner (nbrenner@gwu.edu)

HTML elements that permit user input to the webpage are available as part of the <input> tag.    Full description of them is given in the usual references.   The most important ones are as follows; note that the closing </input> tag can be left out under Internet Explorer:

Permit the user to enter one line of text:

   <input type=“text“ name=“somename1“ value=“Initial text“> 

Permit the user to enter one line of text, which will be covered up by asterisks:

   <input type=“password“ name=“somename2“> 

Permit the programmer (not the user) to enter one line of text, which will not be displayed on screen (but is often used by Javascript programs as a temporary cache):

   <input type=“hidden“ name=“somename3“> 

Display a small square box which can be clicked by the user, to make a check mark appear in it; there must be text beside the box to inform the user what it represents:

   <input type=“checkbox“ name=“somename4“> (Outside text) 

Display a small round button which can be clicked by the user, to make a dot appear in it; there must be text beside the button to inform the user what it represents.  Normally, this button is one of a group, and only one of them can be selected:

   <input type=“radio“ name=“groupname5“ value=“young“ checked=“true“>0-18 

Display a command button which can be clicked by the user, to cause transmission of the user values (see below); the caption of the button informs the user what it represents:

   <input type=“submit“ value=“A caption“> 

Display a command button which can be clicked by the user, typically to invoke a Javascript function.  It does not  transmit the user values; the caption of the button informs the user what it represents:

   <input type=“button“ value=“A caption“> 

Display a text box and command button which can be clicked by the user, in order to bring up a dialog box.  The user selects a file from a File Manager-like list, and its path and name fill the text box:

   <input type=“file“> 

Two other independent tags perform similar functions; why they were not included as type= attributes within the <input> tag is unclear.

   <select name=”somename6″>

     <option value=”A”>Alfred</option>

     <option value=”B”>Bertram</option>

     <option value=”C”>Carol</option>  

   </select> 

   <textarea rows=”6″ cols=”25″ name=”somename7″>

     (Text for the textarea)          

   </textarea> 

(The independent  <button> tag is used only with Javascript.)

The values, texts and selections made by the user with these controls must be transmitted to another webpage for utilization.   (We will see later that they can also be processed on this same webpage with programs written in the Javascript language.)  That transmission occurs when a user control is “clicked” by the user with the mouse.  Most commonly, the type=“submit” command button is the control which is clicked.  In order to know which input control values should be sent, and to where they should be sent, the block of user controls (including the clicked command button) must be part of a form, that is, a region delimited by a pair of tags <form></form>.  The <form> tag pair is optional for the Microsoft Internet Explorer browser, but is required for most other browsers.

  <form action=URL name=“form1“>

  <input type=“text“ value=“(some initial text)“> 

  <input type=“submit“ value=“Push me!“> 

  </form>

As usual, the URL can be the address of another HTML file on the current computer, or it can point to a website anywhere on the internet (and is then prefixed by http://).  By default, the values entered by the user to the input controls within the current form are passed as part of the website address.

__________________________________________________________

Lab:  Create a form like the following, which passes the user”s entries to another webpage.

适用场景：

毕业论文、课程设计、公司项目参考

运行截图

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