There is an optional method within the UserJavaScript.js file named userJavaScriptUpdateBtn(). When this method is present you can return true or false to allow ExtraView to perform additional processing when the Update button is pressed on the edit screen. If this processing returns true, then the submit function continues, but if it returns false, then the update is halted. Typically you will present the user with a message to indicate the error that you want them to correct.
The default code for the method within the UserJavaScript.js file is:
function userJavaScriptUpdateBtn() {
return true;
}
If the method is not present, no error is generated.