function camel (string) {
  if (typeof string === 'string') {
    return string.replace(/([_-][a-z0-9])/ig, ($1) => {
      if (string.indexOf($1) !== 0 && !/[_-]/.test(string[string.indexOf($1) - 1])) {
        return $1.toUpperCase().replace(/[_-]/, '')
      }
      return $1
    })
  }
  return string
}
Given a string, convert snake_case to camelCase
@param {String} string