automatically change form default value if variation is out of stock

This is currently not possible, only one set of defaults can be chosen (or none at all if its a problem for you).

https://github.com/woothemes/woocommerce/blob/06d594311052333dadd877b62142035f0743b9fe/includes/api/class-wc-rest-products-controller.php#L324-L346

Ok. Then is it possible to select automatically the default variation based on in stock item ?

That is no need to set default product variation in back end , when user go to product page then an in stock item automatically select as a default variation using any method like php or javascript etc ?

Yes, this would be possible with some custom code.

You can filter the data here: https://github.com/woothemes/woocommerce/blob/master/includes/api/class-wc-rest-products-controller.php#L599. This is what you are looking to filter in the object: https://github.com/woothemes/woocommerce/blob/master/includes/api/class-wc-rest-products-controller.php#L491

So you’ll essentially need some custom code that looks for and finds a variation with stock. Then you return that variation’s attributes for the default_attributes.

Thank you friend ?? . Could you please give a simple example or sample code . ?

This one is a bit complex for the forums. Consider jobs.wordpress.net to get something custom built.

Ok . No problem . Thank you Mike for the reply .

Hi Tom,

Is there any update regards to this topic? Have you find a solution or code for this? I want to do the same, if variation out of stock the in stock variation will be the default. https://www.ledlam.co.uk
Please update,
Thanks