bemFor.js

/**
 * <p>Create a function that can generate BEM classes based on the specified block.</p>
 * <p>Suppose you have the following code:</p>
 * <pre>
 * const bem = bemFor('my-block');
 * </pre>
 * Then:
 * <ul>
 *     <li><code>bem()</code> will return <code>"my-block"</code></li>
 *     <li><code>bem('my-element')</code> will return <code>"my-block__my-element"</code></li>
 *     <li><code>bem('my-element', 'my-modifier')</code> will return <code>"my-block__my-element my-block__my-element--my-modifier"</code></li>
 *     <li><code>bem(null, 'my-modifier')</code> will return <code>"my-block my-block--my-modifier"</code></li>
 * </ul>
 *
 * @param {string} block the B in BEM
 */
const bemFor = (block) =>
  (element, modifier) =>
    element && modifier ?
      `${block}__${element} ${block}__${element}--${modifier}` :
      element ?
        `${block}__${element}` :
        modifier ?
          `${block} ${block}--${modifier}` :
          block;