AngularJS Essentials

Chapter 3
Understanding the $pristine and $dirty
properties
Sometimes, it would be useful to know whether the field was never touched in order
to trigger (or not) some validation processes. This can be done by the means of two
objects with very suggestive names: $pristine and $dirty.
Pristine means purity, and here, it denotes that the field wasn't touched by anyone.
After it's been touched for the first time, it becomes dirty. So, the value of $pristine
always starts with true and becomes false after any value is typed. Even if the field
is empty again, the value remains false. The behavior of the $dirty object is just the
opposite. It is by default false and becomes true after the first value is typed:
The plate is invalid!
The $error object
In the end, the one that remains is the $error object. It accumulates the detailed list
of everything that happens with the form and can be used to discover which field
must be proofread in order to put the form in a valid situation.
Let's use it to help our users understand what's exactly going wrong with the form:
You must inform the plate of the car!
The plate must have at least 6 characters!
The plate must have at most 10 characters!
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