DetectMQ is based on the post and the ideas on Jeremy Keith's site to make the detection of currently used Media Query easier.

It makes much more sense to keep the Media Queries in only one place and this way you are also able to match the breakpoints accurately in every browser. But there's also more to it than just that: Think of a responsive web application where you need to use different JavaScript when the layout changes. This'll make that much easier.

• 285 bytes minified and gzipped
• Trigger on pageload and window resize
• Custom threshold time before triggering (over 200ms recommended!)

First you specify in CSS a hidden :after pseudo element for body and change the content of that inside every Media Query. You could think of these as the "titles" of your Media Queries. You can have as many of them as you'd like + you can use your own names as long as you don't include any spaces in the name.

body:after {
  content: "narrow";
  display: none;
}
@media screen and (min-width: 40em) {
  body:after {
    content: "normal";
  }
}
@media screen and (min-width: 70em) {
  body:after {
    content: "wide";
  }
}

You have to first specify setting you'd like to use and after that include the JavaScript plugin (Check index.html in this repository). Inside the callback option you use the same "titles" which you used in CSS. live and threshold settings are optional and you can see the defaults below:

var detect_mq = {
  live: true,       // Boolean: Trigger on window resize, true or false
  threshold: 300,   // Integer: Threshold time before triggering (200ms+ recommended), in milliseconds
  callback: function () {

    if (dmq_size == "narrow") {
      // Do something
    }

    if (dmq_size == "normal") {
      // Do something
    }

    if (dmq_size == "wide") {
      // Do something
    }

  }
};

For a demo go to http://viljamis.com/detectmq/

• Explorer 9+
• Explorer 9 mobile
• Safari 5
• iOS 5 Safari
• Chrome 18
• Firefox 3.6+
• Opera 11
• Opera Mini 7
• Opera Mobile 10.1
• Mozilla Mobile (Fennec) 4.0

• v 0.3 No more "work in progress"(!) + Adds check for browsers without proper CSS :after support
• v 0.22 Adds check for browsers without getComputedStyle support, thanks @vesan!
• v 0.21 Prevent script error in older IE's
• v 0.2 Fixes threshold option and adds list of tested browsers
• v 0.1 Initial Release

Doesn't work on IE6-8 (but if needed, the support can be added), iOS 4.3.2, older Android devices and on Symbian 3 Webkit, but if you anyway use mobile first approach this isn't a big problem.

Licensed under the MIT license.

Copyright (c) 2011-2012 Viljami Salminen, http://viljamis.com/

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.

Great! New ideas are more than welcome, but please check the Pull Request Guidelines first before doing so.