点击javascript按钮添加好友

Question

On Facebook you can click on the "add friend" button to add a friend without refreshing the page. Presumably this involves accessing a database using JavaScript, but I was given to understand that that is a bad idea.

Could anyone explain this to me?

Answer 1

This is not directly interacting with the database but with an API ( some web service ). The API then has logic within it to then interact with the database.

Answer 2

Its Ajax basicly

1. User click button
2. Javascript open another page at background like "addfriend.php?id=5"
3. PHP page add request to Database
4. PHP (or any server page) return answer
5. Javascript handle answer

Answer 3

They do not allow database access from javascript, they are simple making HTTP calls from javascript, without loading entire page. The technology is called AJAX (Asynchronous JavaScript and XML). You can read more about AJAX on Wikipedia .

Answer 4

It would have been bad if the SQL for the database would be specified in the client code and executed without any validation against the DB:

<input type="button" onclick="updateDatabase('INSERT INTO FriendRequests...')" />

...but that is not the case.

Very simplified: The 'add friend' button calls a server-side method via an HTTP request. The server-side method verifies your identity and the request, then probably calls a data-access method, and the data-access method then calls the underlying database. So this is perfectly acceptable.

Answer 5

JavaScript导致浏览器在幕后发出HTTP请求 （通常称为Ajax），服务器端进程处理数据库访问。