Passing a callback function to jQuery AJAX success function

Question

I'm trying to pass in a function to run when the AJAX call is successful, however it's not working as it say's that "callback is not a function".

Example:

Calling Code:

getGrades(var);    

JS:

function getGrades(grading_company) {

    // Set file to get results from..
    var loadUrl = "ajax_files/get_grades.php";

    // Set data string
    var dataString = 'gc_id=' + grading_company;

    // Set the callback function to run on success
    var callback = 'showGradesBox';

    // Run the AJAX request
    runAjax(loadUrl, dataString, callback);

}

function showGradesBox(response) {

    // Code here...

}

function runAjax(loadUrl, dataString, callback) {

    jQuery.ajax({
        type: 'GET',
        url: loadUrl,
        data: dataString,
        dataType: 'html',
        error: ajaxError,
        success: function(response) {
            callback(response);
        }
    });    

}

Now if I replace this line below with the function name itself it works:

callback(response);

But I can't get it to work like above where I get the function name from a passed in parameter.

Solution

showGradesBox is a string in your code. So you have two options to execute the callback function:

If you want to keep the string you can use

this[callback](response);

(if callback is defined in global scope you can also use window[callback](response);

Or you can pass the function directly:

var callback = showGradesBox;

(in this case you can keep your existing code for callback execution)