## README: Custom Ninja Forms Field Validation

The accompanying PHP and JS files contain stripped-down controllers that provide support for custom validation logic along with support for asynchronous validation to handle slow/complex or remote/confirmation routines.

For the client-side, this is accomplished by adding a temporary `custom_validation_validating` error to interrupt any attempt to submit the form or move to another part of a multi-part form. This temporary error displays a customizable "Validating…" error message. When the custom validation is complete, if the field is invalid the temporary error is replaced with a corresponding error message.

If the user attempted to submit the form or move to the next part of form, and asynchronous validation is in progress, it will re-attempt the user's action when the asynchronous validation is complete.

Ideally, Ninja Forms would implement replace its synchronous queue of callbacks with a promise-based solution to allow for controllers to take their time with whatever needs to be processed.

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