jQuery Roundup: jPages, youRhere, jquery.lazyLoader, Deferred and Promise in jQuery

31 Jan 2012 | By Alex Young | Tags jquery plugins lazyloading pagination promises
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jPages

jPages (License: MIT, GitHub: luis-almeida / jPages) by Luis Almeida is a client-side pagination plugin that can page through a set of elements in an unordered list. Given some suitable HTML, perhaps containing a list of images:

<!-- Future navigation panel -->
<div class="holder"></div>

<!-- Item container (doesn't need to be an UL) -->
<ul id="itemContainer">
    <!-- Items -->
    <li></li>
    <li></li>
    <li></li>
    <li></li>
    <li></li>
</ul>

Then to get pagination controls the only JavaScript we need to use is $('div.holder').jPages({ containerID : 'itemContainer' });.

The author has written lots of demos, applying the plugin to lazy loading images, or even using titles as links to create sub-navigation for a page.

youRhere

You Are Here

youRhere (License: MIT or GPL, GitHub: fastrd / youRhere) by Daniel Sternlicht transforms pages of text to allow the reader’s progress to be saved. The current mouse position is displayed with an arrow, and clicking on a line will highlight it. This can persist by using localStorage.

Basic usage is just $('#content').yourhere();.

jquery.lazyLoader

jquery.lazyLoader (License: MIT, GitHub: davetayls / jquery.lazyLoader by Dave Taylor aims to make image loading more responsive by loading images based on the browser viewport size. With carefully named images it can work pretty much automatically:

$('a').lazyLoader({
  img: function(url, windowWidth) {
    if (windowWidth >= 768){
      return url.replace(/.(jpg|gif|png)$/i, '-mega.$1'); 
    } else {
      return url;
    }
  }
});

jQuery plugin authors take note! Dave has raised the bar! He’s not only included tests, but he’s also running them through a CI server (davetayls/jquery.lazyLoader)! I’m not saying he’s the first person to do this, but given the amount of plugins we receive at DailyJS with no tests I found it a pleasant surprise.

Deferred and Promise in jQuery

Deferred and promise in jQuery by Edwin Martin is an introduction to the tools jQuery provides for working with these functional concepts.

So what is a deferred and what is the difference with a promise? As you have seen above, a promise is an object that is returned from an asynchronous function. You need a deferred when you write such a function yourself.

Edwin aims to explain how to use promises and $.Deferred, and also explain how they’re different.


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