Mouse move direction events in javascript

mouse move direction events in javascript.js

var last_position = {};

document.onmousemove = function(e) {
    //check to make sure there is data to compare against
    if (typeof(last_position.x) != 'undefined') {

        //get the change from last position to this position
        var deltaX = last_position.x - event.clientX,
        deltaY = last_position.y - event.clientY;

        //check which direction had the highest amplitude and then figure out direction by checking if the value is greater or less than zero
        if (Math.abs(deltaX) > Math.abs(deltaY) && deltaX > 0) {
            // mouse move left
        }
        else if (Math.abs(deltaX) > Math.abs(deltaY) && deltaX < 0) {
            // mouse move right
        }
        else if (Math.abs(deltaY) > Math.abs(deltaX) && deltaY > 0) {
            // mouse move up
        }
        else if (Math.abs(deltaY) > Math.abs(deltaX) && deltaY < 0) {
            // mouse move down
        }
    }

    //set the new last position to the current for next time
    last_position = {
        x : event.clientX,
        y : event.clientY
    };
};