This is a total revamp of original jquery.appear plugin hosted on http://code.google.com/p/jquery-appear/

Check demo page!

This plugin can be used to prevent unnecessary processeing for content that is hidden or is outside of the browser viewport.

It implements a custom appear/disappear events which are fired when an element became visible/invisible in the browser viewport.

    $('someselector').appear(); // It supports optinal hash with "force_process" and "interval" keys. Check source code for details.

    $('<div>test</div>').appear(); // It also supports raw DOM nodes wrapped in jQuery.

    $('someselector').on('appear', function(event, $all_appeared_elements) {
      // this element is now inside browser viewport
    });
    $('someselector').on('disappear', function(event, $all_disappeared_elements) {
      // this element is now outside browser viewport
    });

If you want to fire appear event for elements which are close to vieport but are not visible yet, you may add data attributes appear-top-offset and appear-left-offset to DOM nodes.

    <div class="postloader" data-appear-top-offset="600">...</div> # appear will be fired when an element is below browser viewport for 600 or less pixels

Appear check can be forced by calling $.force_appear(). This is suitable in cases when page is in initial state (not scrolled and not resized) and when you want manually trigger appearance check.

Also this plugin provides custom jQuery filter for manual checking element appearance.

    $('someselector').is(':appeared')

Licensed under MIT license.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.