How to add client side validation to form via FAPI?

Question

I can't figure what to add Client Side Validation for form fields.

'#element_validate' => array('_file_generic_settings_max_filesize'),

I also don't know which value to put for different types of validation such as digit, email etc. '#element_validate' => 'email',

'#element_validate' => array('email'),

it states that it needs to be string not an array.

And after all this documentation doesn't state that how to add validation instead just creating own validation: https://www.drupal.org/node/1324788

The Drupal FAPI doesn't provide clientside validation by default. You either need to add your own, or you need to find contributed modules that handle it for you. — Jaypan, 2 hours ago

user1271930 · Answer 1 · 2016-11-22 14:24:09Z

Solution was to add following for each integer field with form alter:

['#rules'] = array('digit');

And perhaps it was also needed to set 'views_exposed_filters' as a custom form for validation in the settings of Client Side Validation module.

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