EVENT
HANDLER: onChange
onChange
= myJavaScriptCode
Event handler for FileUpload, Select,
Text, TextArea.
The onChange event handler executes the specified JavaScript code
or function on the occurance of a change event. This is when the data
in one of the above form elements is altered by the user. This is used
frequently to validate the data that has been entered by the user by calling
a specified JavaScript function.
The onChange event handler uses the following Event
object properties.
type - this property indicates the type of event.
target - this property indicates the object to which the event
was originally sent.
The following example shows the use of the onChange event handler
to call a JavaScript function that validates the data input by the user
(in this case, the function simply checks wether the entered email address
contains the '@' character and displays a relevant message). Note that
the first line is HTML code and assumes that the text box is on a form
called 'myForm'.
Code:
<INPUT TYPE="text" VALUE="Enter email address"
NAME="userEmail" onChange=validateInput(this.value)>
<script type="text/javascript" language="JavaScript">
this.myForm.userEmail.focus()
this.myForm.userEmail.select()
function validateInput() {
userInput = new String()
userInput = this.myForm.userEmail.value
if (userInput.match("@"))
alert("Thanks for your interest.")
else
alert("Please check your email details are correct
before submitting")
}
</script> |