Angular 4 Form Management
Forms are probably the most crucial aspect of your web application. While we often get events from clicking on links or moving the mouse, it’s through forms where we get the majority of our rich data input from users.
On the surface, forms seem straightforward: you make an input tag, the user fills it out, and hits submit. How hard could it be?
It turns out, forms can be very complex. Here’s a few reasons why:
Form inputs are meant to modify data, both on the page and the server
Changes often need to be reflected elsewhere on the page
Users have a lot of leeway in what they enter, so you need to validate values
The UI needs to clearly state expectations and errors, if any
Dependent fields can have complex logic
We want to be able to test our forms, without relying on DOM selectors
Thankfully, Angular has tools to help with all of these things.
FormControls encapsulate the inputs in our forms and give us objects to work with them
Validators give us the ability to validate inputs, any way we’d like
Observers let us watch our form for changes and respond accordingly
A large category of frontend applications are very form-intensive, especially in the case of enterprise development. Many of these applications are basically just huge forms, spanning multiple tabs and dialogs and with non-trivial validation business logic.
Every form-intensive application has to provide answers for the following problems:
how to keep track of the global form state
know which parts of the form are valid and which are still invalid
properly displaying error messages to the user so that the user knows what to do to make the form valid
All of these are non-trivial tasks that are similar across applications, and as such could benefit from a framework.
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