ITSE 1411 Beginning Web
JS Form Validation Chapter 5 Discussion
Discussion
- Form Validation using onsubmit and onreset event handlers
- The submit button, when pressed, triggers the onsubmit event handler.
- The onsubmit event handler is written inside the form tag.
- The onsubmit event handler is often used to validate the form data.
- The reset button, when pressed, triggers the onreset event handler.
- The onreset event handler is also written inside the form tag.
- The onreset event handler is often used to confirm that the form is to be reset.
- The onsubmit and onreset event handlers often call functions to perform the work needed to validate or confirm that
a form is to be reset. The function called by the onsubmit event handler returns true when the validation is completed
and all elements are valid and a false when any element is not valid. The onreset event handler returns a true when the reset is confirmed
and a false when the reset is cancelled.
- Validating Text and Password Boxes
- Test to see that text boxes and password boxes using the if statement. For numeric fields test with isNaN() method. Return a true when all boxes
validate. Return a false when any box does not validate. It is helpful to use an alert box to show why something does not validate.
- Validating Radio Buttons
- JavaScript creates an array of elements that share the same name, so that a single name=value pair will be submitted when the form is
submitted. The checked property returns a true is selected and a false if not selected.
- Validating Check Boxes
- You may select one or more check boxes in a group. The checked property returns a true when a box is selected and a false when a box
is not selected.
- Validating Selection Lists
- If no selection has been made in a selection list, the selectedIndex property contains a value of -1.