E-commerce website merchandise out of stock button design hide or explain?

In reality, the interface is generally more fixed, where the fixed refers to the position, color, visibility will not change at random, such as light switch, whether or not there is electricity or whether the lights are faulty, the button in the switch will be there, will not disappear.

Switch

However, the network is not the same, you can easily hide a button, or an input box is not editable. There is a lot of risk in doing this, can your design be "self-evident" or "self explanatory"? If not, it is a very important thing for users to make him feel.

For E-commerce sites, when the goods are not goods, the purchase button how to deal with is a very interesting question, hidden? Change to text? Set to not clickable? Change to "arrival notice"?

Purchase button for ecommerce website

When a button is unavailable, is it hidden, or is it preserved and given an explanation? I tend to the latter. Because:
The hidden button is tantamount to creating a "doubt" before giving an explanation;

Keep the button, do some processing on the button (gray, not point), give an explanation, it may be easier to accept the user.

From another aspect, the "buy" button for an ecommerce site, the meaning of existence is not only a normal button, but more like a vane, as if the search engine can not have the "search" button, from the user's habits and feelings, it is not there, you will feel what is missing, the more ordinary users, The more it feels like this.

PS: Above, the European cool practice is reasonable, new eggs and when the more tricky, excellent and jingdong practice is not recommended,