Do can connect database with javascript?

Answer 1

You can't connect directly from a browser to the database, as the browser doesn't have access.
Even if you could, you shouldn't: If your Javascript sends SQL statements to the database, there is nothing stopping a random visitor from having fun by changing your SQL to "drop table", and your entire database is gone.

What you do is setting up a server side web service (using PHP, Java servlets, Ruby on Rails or whatever) that accepts a URL, converts it to a DB query and returns the result as JSON. The primary thing from a security standpoint is that you never insert a string from the web into the SQL without validating it first.

As an example, you could have something like this:

--- browser javascript (using jQuery) ---
$.getJSON("/productDetail.json?productId=123", function (data) {
// do something with the data
});

--- server (using Java servlet) ---
void doProductDetail(HttpServletRequest req, HttpServletResponse res) {
int productId = Integer.parseInt(...); // get product ID from query param
String sql = ...; // generate the SQL
String json = ...; // execute query, convert result to JSON
res.write(json); // send to browser
}

Answer 2

you can use jquery to make a Async, or Sync call to a page method [web method] (in the code behind) which has access to a database.