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JavaScript utility that determines whether an element is completely within the browser viewport

branch: master
README.md

Within Viewport

Determine whether elements are within the viewport

Includes both a standalone, plain JavaScript function and a jQuery plugin with handy selectors and shorthand methods. Both versions are equally functional.

Usage

Basic

// Returns true if the element is entirely within view
var elem = document.getElementById("#myElement");
withinViewport(elem);

Advanced

// Test against only some sides of the viewport for faster performance
withinViewport(elem, {sides: "left"});
// Define your own viewport by specifying thresholds for each side
// Example: element is at least 12px inside the top and right of the viewport
withinViewport(elem, {top: 12, right: 12});

For more options, see Settings section below.

Shorthand notation

// These will use the default thresholds; see 'Settings' section below
withinViewport(elem, "bottom right");
withinViewport.left(elem);

jQuery plugin

Include

The scripts must be included in this order:

<script src="http://code.jquery.com/jquery-1.11.0.min.js"></script>
<script src="withinViewport.js"></script>
<script src="jquery.withinViewport.js"></script>

Usage

Basic

// Returns true if the element is entirely within the viewport
$("#myElement").is(":within-viewport");
// Returns a jQuery object of all <div>s that are within the viewport
$("div").withinViewport();

Advanced

There are shorthand selectors and methods for testing against only one edge of the viewport.

// Returns true if the element is within the left edge of the viewport
// Also works with 'top', 'right', and 'bottom'
$("#myElement").is(":within-viewport-left");
// Returns a jQuery collection of all <div>s within the left edge of the viewport
$("div").withinViewportLeft();
// Same as above, but only elements that are at least 12px inside the left edge
$("div").withinViewportLeft({left: 12});

These shortcuts will result in slightly better performance if you're testing hundreds or thousands of elements.

Live updating

If you're looking to keep tabs on elements' whereabouts at all times, you can bind to the window's resize and scroll events. Instead of scroll, I recommend using James Padolsey's scrollStop event since firing on every window.scroll event will bring your UI to its knees.

$(window).bind("resize scrollStop", function() {
  // Your code here...

  // Example:
  $("div")
    // Declare all divs out of the viewport...
    .removeClass("within-viewport");
    // Then filter them to reveal which ones are still within it
    .filter(":within-viewport")
      .addClass("within-viewport");
});

A future version will allow you to fire custom events when elements pass in and out of the viewport.

Settings

This applies to both the jQuery plugin and standalone function.

Use the object withinView.defaults to define your page's practical viewport compared to the actual browser viewport.

For example, a fixed header with a height of 100px that spans the entire width of the page effectively lowers the viewport by 100px from the top edge of the browser window:

withinView.defaults.top = 100;

If you only care about some edges of the viewport, you can specify them to improve performance:

withinView.defaults.sides = "left bottom";

You can also pass settings on the fly to temporarily override the defaults:

withinViewport(elem, {sides:"left bottom", left: 40});
$("div").withinViewport({sides:"left bottom", left: 40});

Individual elements may have their own settings embedded in a data attribute using object notation. These will override both the defaults any any settings passed to the function on the fly (like the example above).

<div data-withinviewport-settings="{sides: 'left', top: 40}">

You can specify negative threshold values to allow elements to reside outside the viewport.

What's Next

  • Option to fire events when elements pass in and out of the viewport
  • Test against Firefox 3.6, Safari 5.0.1
  • Support IE7

No IE6 support is planned — if you'd like to add it, feel free to make a pull request.

Credit

Within Viewport is inspired by these similar utilities which only reflect whether an element is at least partially in view:

History

0.2 - November 5, 2011

  • Standalone version now available, no jQuery or other dependencies
  • Cleaned up and standardized the jQuery plugin
  • Added optional shortcut methods
  • Added support for testing multiple sides at once (eg, left and bottom)
  • Removed requirement for Array.forEach and replaced with faster while() loops
  • Tested against IE8-9, Firefox 7, Chrome 15, Safari 5.1, Opera 11.52; Mac & Windows
  • Included a demo

0.1 - October 15, 2011

  • Initial beta version

License

Have fun with it — BSD, MIT, or GPL; see included LICENSE file

Author

Craig Patik, patik.com & @craigpatik

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