Javascript fixed-top navbar only after scrolling

问题

Does anyone know what javascript effects are being used to create the navbar effect on lesscss.org where the navbar only becomes fixed to the top after scrolling beyond a certain point. If anyone has actual code examples, or links to tutorials, that'd be appreciated.

回答1:

it's a javascript check using the window.onscroll event

in the HTML source near the top:

window.onscroll = function () {
    if (!docked && (menu.offsetTop - scrollTop() < 0)) {
      menu.style.top = 0;
      menu.style.position = 'fixed';
      menu.className = 'docked';
      docked = true;
    } else if (docked && scrollTop() <= init) {
      menu.style.position = 'absolute';
      menu.style.top = init + 'px';
      menu.className = menu.className.replace('docked', '');
      docked = false;
    }
};

来源：https://stackoverflow.com/questions/12849533/javascript-fixed-top-navbar-only-after-scrolling