Question

I want a popup to be displayed when user reaches a certain document height. For instance when reader approaches ~end of a post a popup can be triggered asking his/her input (comment whether liked post or not)
I tried fetching/passing document height via:

function doch() {
    var currentscrollpos;
    if (currentscrollpos > 1500) { 
        //trigger popup
        alert(currentscrollpos);
    }
    setInterval(function() {
        currentscrollpos = $(document).scrollTop();
        return currentscrollpos;
    }, 3e3);
}​

in html function can be simply triggered via doch();

The problem is, that the value of currentscrollpos can’t be passed from setInterval function to if loop?

Answer 1

Why use setInterval if you can bind to when a user scrolls down the page?

$(window).scroll(function(){ //when a user scrolls
    if(this.pageYOffset + $(this).height() > $(document).height() - 200){ //if the scroll is within 200 px of the bottom of the page
        $('div').css('background', 'red'); //do popup
    }
});

http://jsfiddle.net/rUbwq/2/