If there’s one thing nearly all contemporary, interactive client-side web applications have in common, it’s a reliance on dynamic user-facing text input fields. These fields play the all-important role of capturing plain text data from client-side browsers and sharing that information with a server-side application, allowing that application to perform specific actions with that data based on stringent request parameters. We encounter these fields when we log into or register a new account within an application, query content from a web application’s database, fill out a contact form, write comments on an article post, and more.
When we interact with these fields as client-side users, we might notice that some fields only accept data in a certain format. For example, if we enter integers into a “First Name” or “Last Name” field, we’ll likely receive an error response from the application quickly notifying us that integers aren’t valid in that field. Similarly, if we enter our name into a field that asks for our date of birth, we’ll likely receive an error response that asks for valid integers instead.