bemify-single.js

export function bemify(block, modifiers) {
  if (!modifiers) {
    return block;
  }

  if (typeof modifiers == 'object' && !Array.isArray(modifiers)) {
    modifiers = Object.keys(modifiers).filter(modifier => modifiers[modifier])
  }

  if (typeof modifiers == 'string') {
    modifiers = modifiers.split(' ')
  }

  return block + ' ' + modifiers.map(modifier => `${block}--${modifier}`).join(' ');
}

console.log(bemify('button', null))
// button

console.log(bemify('button', []))
// button

console.log(bemify('button', 'red close'))
// button button--red button--close

console.log(bemify('button', ['red', 'close']))
// button button--red button--close

console.log(bemify('button', {
  red: true,
  close: true,
  nope: false
}))
// button button--red button--close