The markup Readmore.js requires is so simple, you can probably use it with your existing HTML—there’s no need for complicated sets of div’s or hardcoded classes, just call .readmore() on the element containing your block of text and Readmore.js takes care of the rest. Readmore.js plays well in a responsive environment, too.

Readmore.js is tested with—and supported on—all versions of jQuery greater than 1.9.1. All the “good” browsers are supported, as well as IE10+; IE8 & 9 should work, but are not supported and the experience will not be ideal.

Install

Install Readmore.js with npm:

$ npm install readmore-js

Then include it in your HTML:

<script src="/node_modules/readmore-js/readmore.min.js"></script>

Or, using Webpack or Browserify:

require('readmore-js');

Use

$('article').readmore();

It’s that simple. You can change the speed of the animation, the height of the collapsed block, and the open and close elements.

$('article').readmore({
  speed: 75,
  lessLink: '<a href="#">Read less</a>'
});

The options:

• speed: 100 in milliseconds
• collapsedHeight: 200 in pixels
• heightMargin: 16 in pixels, avoids collapsing blocks that are only slightly larger than collapsedHeight
• moreLink: '<a href="#">Read more</a>'
• lessLink: '<a href="#">Close</a>'
• embedCSS: true insert required CSS dynamically, set this to false if you include the necessary CSS in a stylesheet
• blockCSS: 'display: block; width: 100%;' sets the styling of the blocks, ignored if embedCSS is false
• startOpen: false do not immediately truncate, start in the fully opened position
• beforeToggle: function() {} called after a more or less link is clicked, but before the block is collapsed or expanded
• afterToggle: function() {} called after the block is collapsed or expanded
• blockProcessed: function() {} called once per block during initilization after Readmore.js has processed the block.

If the element has a max-height CSS property, Readmore.js will use that value rather than the value of the collapsedHeight option.

The callbacks:

The beforeToggle and afterToggle callbacks both receive the same arguments: trigger, element, and expanded.

• trigger: the “Read more” or “Close” element that was clicked
• element: the block that is being collapsed or expanded
• expanded: Boolean; true means the block is expanded

The blockProcessed callback receives element and collapsable.

• element: the block that has just been processed
• collapsable: Boolean; false means the block was shorter than the specified minimum collapsedHeight—the block will not have a "Read more" link

Callback example:

Here’s an example of how you could use the afterToggle callback to scroll back to the top of a block when the “Close” link is clicked.

$('article').readmore({
  afterToggle: function(trigger, element, expanded) {
    if(! expanded) { // The "Close" link was clicked
      $('html, body').animate( { scrollTop: element.offset().top }, {duration: 100 } );
    }
  }
});

Removing Readmore:

You can remove the Readmore.js functionality like so:

$('article').readmore('destroy');

Or, you can be more surgical by specifying a particular element:

$('article:first').readmore('destroy');

Toggling blocks programmatically:

You can toggle a block from code:

$('article:nth-of-type(3)').readmore('toggle');

CSS:

Readmore.js is designed to use CSS for as much functionality as possible: collapsed height can be set in CSS with the max-height property; “collapsing” is achieved by setting overflow: hidden on the containing block and changing the height property; and, finally, the expanding/collapsing animation is done with CSS3 transitions.

By default, Readmore.js inserts the following CSS, in addition to some transition-related rules:

selector + [data-readmore-toggle], selector[data-readmore] {
  display: block;
  width: 100%;
}

selector would be the element you invoked readmore() on, e.g.: $('selector').readmore()

You can override the base rules when you set up Readmore.js like so:

$('article').readmore({blockCSS: 'display: inline-block; width: 50%;'});

If you want to include the necessary styling in your site’s stylesheet, you can disable the dynamic embedding by setting embedCSS to false:

$('article').readmore({embedCSS: false});

Media queries and other CSS tricks:

If you wanted to set a maxHeight based on lines, you could do so in CSS with something like:

body {
  font: 16px/1.5 sans-serif;
}

/* Show only 4 lines in smaller screens */
article {
  max-height: 6em; /* (4 * 1.5 = 6) */
}

Then, with a media query you could change the number of lines shown, like so:

/* Show 8 lines on larger screens */
@media screen and (min-width: 640px) {
  article {
    max-height: 12em;
  }
}

Contributing

Pull requests are always welcome, but not all suggested features will get merged. Feel free to contact me if you have an idea for a feature.

Pull requests should include the minified script and this readme and the demo HTML should be updated with descriptions of your new feature.

You’ll need NPM:

$ npm install

Which will install the necessary development dependencies. Then, to build the minified script:

$ gulp compress