classes.js

export const classes = (...args) => {
  return args
    .map((arg) => {
      if (arg === null || arg === undefined) return null
      return typeof arg === 'string'
        ? arg
        : Object.keys(arg)
            .filter((key) => arg[key])
            .join(' ')
    })
    .filter(Boolean)
    .join(' ')
}

classes('a', 'b', { fill: true, disable: false }) // "a b fill"