Javascript provides the ability to create custom errors by modifying the prototype of a function to the Error protorype. This is how one would create a custom error:
function ValidationError(message) {
this.name = 'ValidationError';
this.message = message;
}
ValidationError.prototype = Error.prototype;
// USAGE
throw new ValidationError('the form is invalid');To catch it you can check the class of an error using
instanceof:
try {
// do stuff
throw new ValidationError('the form is invalid');
} catch (ex) {
if (ex instanceof ValidationError) {
alert(ex.message); // the form is invalid
} else {
// crash and burn
throw ex;
}
}