固定 div 滚动

Question

I'm trying to create a div which will get a class only on scrolling and when the value of scroll is 210. I have next code :

$(document).ready(function() {
    var pageWidth = $(window).width();

    if(pageWidth > 700){
        var contentLeft = $('#content-left');
        var height = 210;

        $(window).scroll(function () {
            if ($(window).scrollTop() < height) {
                contentLeft.attr('class', 'content-left');
            } else {
                contentLeft.attr('class', 'content-left leftContentFixed');
            }
        });
    }
});

I try to apply this only on desktops. Thus, I do not need the class leftContentFixed if it's on a smartphone or tablet.

If I try something like :

$(document).ready(function() {
    var pageWidth = $(window).width();

    if(pageWidth > 700){
        alert("Bigger than 700");
    }else{
        alert("Smaller than 700");
    }
});

Than it works perfect, but with my code it isn't working. The class leftContentFixed is added although the screen is smaller than 700.

Any advice?

Answer 1

You need to check screen size on resize event and check for its value when user scrolls the page. You could create mobile variable and make it true/false depends on screen size, then in scroll callback check for its value and choose correct class.

 $(document).ready(function() { var pageWidth = $(window).width(), height = 210, contentLeft = $('.content-left'), mobile = false; $(window).on('load resize', function() { pageWidth = $(this).width(); // Save mobile status if (pageWidth > 700) { mobile = false; } else { mobile = true } }) $(window).on('scroll', function() { if ($(window).scrollTop() > height) { // Set default class var _class = 'content-left leftContentFixed'; // If mobile then modify class if (mobile) { _class = 'content-left'; } contentLeft.attr('class', _class); } else { var _class = 'content-left'; contentLeft.attr('class', _class); } }); });

 html { height: 2000px } .content-left { background: gold; width: 50px; height: 100px; } .content-left.leftContentFixed { position: fixed; top: 0; }

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <div class="content-left"></div>