/*
 * @param variable The variable you want to get the type of
 * @returns 'string', 'number', 'array', 'function', or 'object'
 */
function type (variable) {
  return Object.prototype.toString.call(variable).slice(8, -1).toLowerCase()
}

/**
 * Checks if a variable matches the expected format at every level. This includes checking that any given object has the
 * same keys as expectedFormat.
 * @param variable The variable to check
 * @param expectedFormat 'string', 'number', 'function', or javascript object/array that contains any of these items.
 * Example expected object: {
 *   shoppingList: [
 *     {
 *       name: 'string',
 *       quantity: 'number'
 *     }
 *   ],
 *   friendNames: ['string']
 * }
 * @returns boolean true if variable matches the expected format, false otherwise
 */
function valid (variable, expectedFormat) {
  switch (type(variable)) {
    case 'object':
      if (
        type(expectedFormat) !== 'object' ||
        !Object.keys(expectedFormat).every(prop => variable.hasOwnProperty(prop))
      ) {
        return false
      }
      return Object.keys(expectedFormat).every(key => valid(variable[key], expectedFormat[key]))

    case 'array':
      if (type(expectedFormat) !== 'array') {
        return false
      }
      return variable.every(item => valid(item, expectedFormat[0]))

    case 'string':
      return expectedFormat === 'string'

    case 'number':
      return expectedFormat === 'number'

    case 'function':
      return expectedFormat === 'function'

    default:
      console.log(`UnexpectedFormat type '${type(expectedFormat)}'`)
      return false // Unexpected type
  }
}