Add quantity button (+/-) which change based on minimum quantity

[seelk]

Hi guys!

I have issue which I cannot resolve. I have some products in my shop which have differents quantity (I added plus&minus button) and when my product is sold per 1 item I can add and remove but when I set minimum quantity of some product to 10 item as minimum and customer click on plus button the amount should will be 20 not 11.

 

I don't know how to set to variable minimum quantity of product, I tried but it isn't working...

var minimalPurchase = $('#quantity_wanted').val();

I use the feature from this website: http://jsfiddle.net/laelitenetwork/puJ6G/

 

Prestashop version: 1.5.3.1