sebmck/6to5

// @flow
import { FLIPPED_ALIAS_KEYS, ALIAS_KEYS } from "../definitions";

/**
 * Test if a `nodeType` is a `targetType` or if `targetType` is an alias of `nodeType`.
 */
export default function isType(nodeType: ?string, targetType: string): boolean {
  if (nodeType === targetType) return true;

  // This is a fast-path. If the test above failed, but an alias key is found, then the
  // targetType was a primary node type, so there's no need to check the aliases.
  if (ALIAS_KEYS[targetType]) return false;

  const aliases: ?Array<string> = FLIPPED_ALIAS_KEYS[targetType];
  if (aliases) {
    if (aliases[0] === nodeType) return true;

    for (const alias of aliases) {
      if (nodeType === alias) return true;
    }
  }

  return false;
}