How can I implement custom validation functions in my application?

How can I implement custom validation functions in my application?

You can create custom validation functions by defining a function that checks the input against your criteria. What framework are you using?

I'm using React. Can you give me an example?

Sure! In React, you can create a function like this:

function validateEmail(email) {
    const re = /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/;
    return re.test(String(email).toLowerCase());
}

You can then use this function in your form validation.

What if I want to validate multiple fields?

You can create a validation object that holds multiple validation functions, and then iterate over the fields to validate them. Would you like a code example for that?