如何将sql查询结果传递给javascript函数？

Question

hello I wanted to know whats the best way to send sql results to a javascript function. I have two dropdown lists and i want to populate the second one according to the first one. both dropdown lists arre populated from a mysql database. fillcourses is the javascript function but i dont know how to pass the result array to it.

$db = new Db();
    $db->query('SELECT idDepartment,name FROM department');
    <select name="department" onchange=" fill_courses (
        SELECT courseNumber,courseId FROM courses 
        WHERE Department_idDepartment = document.addCourse.department.selectedIndex.value); ">';
        while ($row=$db->nextRow())
        {
            echo'<option value="' . $row['idDepartment'] . '">' . $row['name'] . '</option>';
        }
        echo'</select>
        <select name="courses">
        </select>

Answer 1

You may want to consider between two main options:

1. Either generate the JavaScript code on the server-side in PHP just before the response is sent to the browser. In this case, you will have all the data held within the browser. This will be very fast, but it is only feasible if you do not have a large amount of data to populate your drop-downs with.

2. You could also use Ajax, so that when you change the value of your first drop-down your browser will initiate an asynchronous request to your server, which in turn will respond with the data to populate your second drop-down. You may want to use a JavaScript library such as jQuery to help you with this from the browser-side.