mouse speed javascript function

Question

Working on some javascript. I found a pretty good function that calculates the speed of the cursor. The problem is that i want to return the actual value, not a callback. How would you do that?

        function makeVelocityCalculator(e_init, callback) {
        var x = e_init.clientX,
            y = e_init.clientY,
            t = Date.now();
        return function(e) {
            var new_x = e.clientX,
                new_y = e.clientY,
                new_t = Date.now();
            var x_dist = new_x - x,
                y_dist = new_y - y,
                interval = new_t - t;
            // update values:
            x = new_x;
            y = new_y;
            t = new_t;
            var velocity = Math.sqrt(x_dist*x_dist+y_dist*y_dist)/interval;
            callback(velocity);
        };
    }

Answer 1

well , then change that function to return velocity, instead of "callback(velocity)"

Js Fiddle sample

Or you can use it the way it was intended

makeVelocityCalculator(initialEvent, function(velocity) {
   console.log("velocity is", velocity);
});
is pretty much same as 
var velocity = makeVelocityCalculator(initialEvent);
console.log("velocity is", velocity);