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bem-core library Build Status GitHub Release devDependency Status

Documentation on bem-core in a much more informative way is also available at bem.info. 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 bem.info. E.g. JSDoc for i-bem is here https://en.bem.info/platform/libs/bem-core/current/desktop/i-bem/#jsdoc


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., v4):

    $ git clone -b v4 git://github.com/bem/bem-core.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.