For legacy browsers, it's possible to use a polyfill such as Hyperform to compensate for the lack of support for the constraint validation API.Because you're already using Java Script, using a polyfill isn't an added burden to your website or web application's design or implementation.The message is shown to the user when reporting the problem.If the argument is the empty string, the custom error is cleared.From that you should be able to figure out what the problem is with your IF condition.Form validation is natively supported by the browser, but sometimes different browsers will handle things in a manner which makes relying on it a bit tricky. Let’s look at the HTML first: is a temporary URL that would point to something real on a server someplace (where you have backup server-side validation of course).Also note we fire the validation on submit rather than as every field is modified.The final thing to note is that each of the three fields has a corresponding logic (which is run on submit remember) checks for name and age only as movie is optional. Don’t forget that on a successful submission it’s going to POST to a temporary URL.
This lets you use Java Script code to establish a validation failure other than those offered by the standard constraint validation API.
The user is asked to spend a “budget” for a set of features for a new Star Destroyer model. My check Form method now just needs to see if the total is 100 and that’s it.
You can play with this here: See the Pen form validation 3 by Raymond Camden (@cfjedimaster) on Code Pen.
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.
Even when validation is supported perfectly, there may be times when custom validations are needed and a more manual, Vue-based solution may be more appropriate. Beneath that there is a paragraph that shows or hides itself based on an error state.