HTML XHTML Forms Jan 14 2019 What are forms form is just another kind of XHTML HTML tag Forms are used to create rather primitive GUIs on Web pages Usually the purpose is to ask the user for information The information is then sent back to the server A form is an area that can contain form elements The syntax is form parameters form elements form Form elements include buttons checkboxes text fields radio buttons drop down menus etc Other kinds of tags can be mixed in with the form elements A form usually contains a Submit button to send the information in he form elements to the server The form s parameters tell JavaScript how to send the information to the server there are two different ways it could be sent Forms can be used for other things such as a GUI for simple programs 2 Forms and JavaScript The JavaScript language can be used to make pages that do something You can use JavaScript to write complete programs but Usually you just use snippets of JavaScript here and there throughout your Web page JavaScript code snippets can be attached to various form elements For example you might want to check that a zipcode field contains a 5 digit integer before you send that information to the server Microsoft calls its version of JavaScript active scripting Forms can be used without JavaScript and JavaScript can be used without forms but they work well together JavaScript for forms is covered in a separate lecture 3 The form tag The form arguments form tag encloses form elements and probably other elements as well The arguments to form tell what to do with the user input action url Form data is sent as a URL with form data info appended to the end Can be used only if data is all ASCII and not more than 100 characters method post Specifies where to send the data when the Submit button is clicked method get default required Form data is sent in the body of the URL request Cannot be bookmarked by most browsers target target Tells where to open the page sent as a result of the request target blank means open in a new window target top means use the same window 4 The input tag Most but not all form elements use the input tag with a type argument to tell which kind of element it is type can be text checkbox radio password hidden submit reset button file or image Other common input tag arguments include name the name of the element id a unique identifier for the element value the value of the element used in different ways for different values of type readonly the value cannot be changed disabled the user can t do anything with this element Other arguments are defined for the input tag but have meaning only for certain values of type 5 Text input t field input type text name textfield value with an initial val ulti line text field textarea name textarea cols 24 rows 2 Hello textarea assword field input type password name textfield3 value secret Note that two of these use the input tag but one uses textarea 6 Buttons A submit button input type submit name Submit value Submit A reset button input type reset name Submit2 value Reset A plain button input type button name Submit3 value Push Me submit send data reset restore all form elements to their initial state button take some action as specified by JavaScript Note that the type is input not button 7 Radio buttons Radio buttons br input type radio name radiobutton value myValue1 male br input type radio name radiobutton value myValue2 checked checked female If two or more radio buttons have the same name the user can only select one of them at a time This is how you make a radio button group If you ask for the value of that name you will get the value specified for the selected radio button As with checkboxes radio buttons do not contain any text 8 Labels In many cases the labels for controls are not part of the control input type radio name gender value m male In this case clicking on the word male has no effect A label tag will bind the text to the control label input type radio name gender value m male label Clicking on the word male now clicks the radio button w3schools says that you should use the for attribute label for lname Last Name label input type text name lastname id lname In my testing Firefox and Opera this isn t necessary but it may be for some browsers Labels also help page readers read the page correctly Some browsers may render labels differently 9 Checkboxes A checkbox input type checkbox name checkbox value checkbox checked checked type checkbox name used to reference this form element from JavaScript value value to be returned when element is checked Note that there is no text associated with the checkbox Unless you use a label tag only clicking on the box itself has any effect 10 Drop down menu or list A menu or list select name select option value red red option option value green green option option value BLUE blue option select Additional arguments size the number of items visible in the list default is 1 multiple if set to true or just about anything else any number of items may be selected if omitted only one item may be selected if set to false behavior depends on the particular browser 11 Hidden fields input type hidden name hiddenField value nyah lt right there don t you see it What good is this All input fields are sent back to the server including hidden fields This is a way to include information that the user doesn t need to see or that you don t want her to see The value of a hidden field can be set programmatically by JavaScript before the form is submitted 12 A complete example html head title Get Identity title meta http equiv Content Type content text html charset iso 8859 1 head body p b Who are you b p form method post action p Name input type text name textfield p p Gender label input type radio name gender value m Male label label input type radio name gender value f Female label p form body html 13 The End 14
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