Error - JavaScript
to define your own error types deriving from error to be able to throw new myerror() and use instanceof myerror to check the kind of error in the exception handler.
... way to extend error in javascript?" on stackoverflow for an in-depth discussion.
...on.
...And 8 more matches

PromiseWorker.jsm
iteration is deprecated).
...nd throw your own custom error objects as needed.
...rror is caught by abstractworker, tomsg method will be called to convert it into message.
...And 6 more matches

<input>: The Input (Form Input) element - HTML: Hypertext Markup Language
e attributes are present, with the exception of required, and empty string will not lead to an error.
...e interface contains the badinput, valid, and customerror boolean readonly properties.

Client-side form validation - Learn web development
ding on the error, which lets you apply a specific style to invalid elements.

ValidityState - Web APIs
ue fails to validate, if it's not valid.