The message is shown to the user when reporting the problem.If the argument is the empty string, the custom error is cleared.Let's see how to use this API to build custom error messages.First, the HTML: attribute to turn off the browser's automatic validation; this lets our script take control over validation.Form validation helps us to ensure that users fill out forms in the correct format, making sure that submitted data will work successfully with our applications.
If the information is correct, the application allows the data to be submitted to the server and (usually) saved in a database; if the information isn't correct, it gives you an error message explaining what needs to be corrected.The code is taken from the Stack Overflow question, How to validate email address in Java Script? This is an awesome question because it makes your most intense Facebook political/religious argument look like a slight disagreement over who makes the best beer. Here is the HTML, even though it’s really close to the first example. You can play with this example here: See the Pen form validation 2 by Raymond Camden (@cfjedimaster) on Code Pen. This tells Vue to cast the value to a number when you use it.For the third example, we’ve built something you’ve probably seen in survey apps. However, there is a bug with this feature such that when the value is blank, it turns back into a string. To make it a bit easier for the user, we also added a current total right below so they can see, in real time, what their total is. We set up the total value as a computed value, and outside of that bug I ran into, it was simple enough to setup.You can run this demo below: See the Pen form validation 4 by Raymond Camden (@cfjedimaster) on Code Pen.
While this cookbook entry focused on doing form validation “by hand”, there are, of course, some great Vue libraries that will handle a lot of this for you.
Also note we fire the validation on submit rather than as every field is modified.