2.9.1 • Public • Published

bem-core library Build Status GitHub Release

Documentation on bem-core in a much more informative way is also available at It is also available in Russian.

What is this?

bem-core is a base library for web interface development. It provides the minimal stack for coding client-side JavaScript and templating.


The easiest way to run a project with bem-core is to use the project-stub.

You can use any other way you are familiar with to include the library into the project.



  • common.blocks — suited for any devices and browsers
  • desktop.blocks — should be used for desktop browsers
  • touch.blocks — implement some touch-platforms specifics


  • i-bem — base block with helpers for JS and HTML
  • strings — helpers for JS-strings
  • objects — helpers for JS-objects
  • functions — helpers for JS-functions
  • events — JS-events
  • querystring — helpers for work with querystring
  • tick — global timer
  • idle — IDLE event
  • next-tick — polyfill for nextTick/setTimeout(0, ...)
  • inherit — OOP helpers
  • jquery — jQuery
  • clearfix — CSS clearfix trick
  • identify — identify JS-objects
  • cookie — helpers for work with browser cookies
  • vow — Promises/A+ implementation
  • dom — helpers for work with DOM
  • loader — loader for JS files
  • ua — browser features detection
  • keyboard — keyboard helpers
  • page — html/head/body scaffold


  • vanilla.js + browser.js
  • bemhtml
  • bemtree


The autogenerated JSDoc API can be found on E.g. JSDoc for i-bem is here


You can check the changelog at the Changelog page.


If you used BEM before, check the migration instructions.


Working copy

  1. Get the needed version code (e.g., v2):

    $ git clone -b v2 git://
    $ cd bem-core
  2. Install the dependencies:

    $ npm install

    You need export PATH=./node_modules/.bin:$PATH or an alternative way to run locally-installed npm dependencies.

  3. Install all necessary libraries:

    $ npm run deps
  4. Build and run tests (specs):

    $ npm test
  5. Run development server:

    $ npm start

How to contribute

Please refer to How to contribute guide.

Modular testing

A default test bundle for functions__debounce:

$ magic make desktop.specs/functions__debounce

You can see the results of the tests in the terminal after the building process finishes.

You can also watch them in a browser loading desktop.specs/functions__debounce/spec-js+browser-js+bemhtml/spec-js+browser-js+bemhtml.html.

Run tests for other BEM entities in the same way. This will work for those which are equipped with .spec.js file.

Code coverage

To build code coverage report add ISTANBUL_COVERAGE=yes environment variable to the tests run command:

$ ISTANBUL_COVERAGE=yes magic make desktop.specs && istanbul report html

You can run modular testing with coverage as well by using more concrete build target as was described above.

$ ISTANBUL_COVERAGE=yes magic make desktop.specs/functions__debounce && istanbul report html

After tests finish, you can view coverage HTML report by opening coverage/index.html in your favorite browser.

The whole code coverage statistics can be found on the bem-core profile page on Coveralls.

Tests are built with a enb-bem-specs library. Check the details (available in Russian only).

Supported browsers

Our browser support policy is based on statistics we get from Yandex services.

Browsers with more than 2% users get full compliant support, more than 0.5% — partially compliant (which means that data is accessible but not necessary 100% functional). New features testing is not provided by us for  browsers with less than 0.5% users.


Fully compliant

  • Google Chrome 29+
  • Firefox 24+
  • Yandex 1.7+
  • Opera 12.16
  • MSIE 10.0
  • MSIE 9.0
  • MSIE 8.0
  • Opera 12.15

Partially compliant

  • Opera 17.0
  • Opera 16.0
  • Opera 12.14
  • Opera 12.2
  • Firefox 23


Fully compliant

  • iOS 6+
  • Android 2.3+
  • Opera Mobile 12+
  • Windows Phone 7+

Partially compliant

  • iOS 5
  • Android 2.2


Code and documentation copyright 2012 YANDEX LLC. Code released under the Mozilla Public License 2.0.



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