CODEWITHSUNDEEP
javascriptjqueryperformancesettimeoutzepto
Daniel Hallqvist
Daniel Hallqvist

Reputation: 822

Perfomance of timeout functions

I have a JS-problem where I have to check a horizontal ul for when the li's of that lists width has gone over a max-width, and then reduce the side-padding of those elements to make all li's fit.

The problem is that I can not fire an event when a li is added, simply because I can't control all the code that adds li's to the ul.

So my option has been to loop the check of the li's total width a few times a second, something like this:

function UpdateNavBar(initialX) { 
        var w = 0;
        var maxW = 100;
        var visibleLis = $(".navigationbar ul li.menuitem");
        $.each(visibleLis, function (i, e) {
            return w += $(e).width();
        });
        if (w >= maxW) {
            --xPadding;
            $(".navigationbar ul li.menuitem a").css({ "padding-left": xPadding, "padding-right": xPadding });

        }

        w = 0;
        setTimeout(UpdateNavBar, 100, initialX);
    }
    var xPadding = parseInt($(".navigationbar ul li.menuitem a").css("padding-left").replace("px", ""));
    UpdateNavBar(xPadding);​

My questions are: Is there any other obvious ways to achieve this that I'm missing? How will a function like this affect perfomance of a site, keeping in mind that it is meant to be ran on all kinds of devices?

Thanks a lot.

Upvotes: 0

Views: 158

Answers (1)

xiaohao
xiaohao

Reputation: 272

em, since you didn't know when a li is added, a loop of settimeout is a not a bad way.

but you can make some optimization.

settimeout will add a handler to the ui thread, so if the time the handler finish executing is short enough, it will result in a better perfomance.

so, my choice is like above code, maybe you can do better

var listLength; 
function UpdateNavBar(initialX) { 
    var w = 0;
    var maxW = 100;
    var visibleLis = $(".navigationbar ul li.menuitem");
    //make a momorize and if no change happen, do nothing
    if(length === visibleLis.length){
        return false;
    }else{
        listLength = visibleLis.length;
    }
    $.each(visibleLis, function (i, e) {
        return w += $(e).width();
    });
    if (w >= maxW) {
        --xPadding;
        $(".navigationbar ul li.menuitem a").css({ "padding-left": xPadding, "padding-right": xPadding });

    }

    w = 0;
    setTimeout(UpdateNavBar, 100, initialX);
}
var xPadding = parseInt($(".navigationbar ul li.menuitem a").css("padding-left").replace("px", ""));
UpdateNavBar(xPadding);​

Upvotes: 1

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