Using "+=variable" does not work as jQuery.animate target value?

Question

I'm creating a sliding image gallery using jQuery and when given a numeric value the "left" css property works fine, but when given a variable it doesn't do anything. Here's my code:

$(document).mousemove(function(e) {
    var gall = document.getElementById("Gallery");
    var gallOffset = $("div#GalleryHold").offset();
    var offsetX = e.pageX - gallOffset.left;
    var left = gall.style.posLeft;
    var pos = offsetX;
    if (mouseIsOver == true) {
        $('#status').html(offsetX + " " + left + " " + mouseIsOver);
        if (offsetX < 400 && left < 0) {
            $("div#Gallery").stop().animate({
                left: '+=pos'
            }, 600);
        }
        if (offsetX > 600 && left > -1100) {
            $("div#Gallery").stop().animate({
                left: '-=pos'
            }, 600);
        }
    }
    else if (mouseIsOver == false) {
        $('#status').html(offsetX + " " + left + " " + mouseIsOver);
    }
});

are you saying animate({left: '+=pos'} doesnt work?

Jon Taylor
– Jon Taylor

2012-07-13 21:06:54 +00:00
Commented Jul 13, 2012 at 21:06 — Jon Taylor
– Jon Taylor, Commented Jul 13, 2012 at 21:06
Try {left: '+=' + pos}

sachleen
– sachleen

2012-07-13 21:07:54 +00:00
Commented Jul 13, 2012 at 21:07 — sachleen
– sachleen, Commented Jul 13, 2012 at 21:07

Gareth · Accepted Answer · 2012-07-13 21:07:44Z

7

'+=pos' is a constant string.

You probably want '+=' + pos, which will evaluate to a string like '+=50'

answered Jul 13, 2012 at 21:07

Gareth

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2 Comments

MrOBrian Over a year ago

Same with the '-=pos' line a few lines down, should also be changed to '-=' + pos

Gareth Over a year ago

@TaylorBishop - If you click the green tick by this answer it will mark it as accepted. This will a) tell other people who find this question that you thought it was the right answer, b) give you a small reputation boost as a reward for giving useful feedback and c) contribute to your "% answered" statistic which hints to other users how responsive you are to the answers they give you :)

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