Function createDictionaryConverter

lib/internal/webidl.js:688–765

* Creates a converter for a Web IDL dictionary type. * @see https://webidl.spec.whatwg.org/#js-dictionary * @param {string} dictionaryName Dictionary identifier. * @param {DictionaryMember[]|DictionaryMember[][]} members Dictionary members, * either for a single dictionary or grouped from leas

(
  dictionaryName,
  members,
)

 * @returns {Converter}
 */
function createDictionaryConverter(
  dictionaryName,
  members,
) {
  const compareMembers = (a, b) => {
    if (a.key === b.key) {
      return 0;
    }
    return a.key < b.key ? -1 : 1;
  };

  const dictionaries = ArrayIsArray(members[0]) ? members : [members];
  const sortedDictionaries = [];

  // Web IDL dictionary conversion steps 3-4 process inherited dictionaries
  // from least-derived to most-derived and sort only within each dictionary.
  // Callers with inheritance pass one member array per dictionary level.
  for (let i = 0; i < dictionaries.length; i++) {
    ArrayPrototypePush(
      sortedDictionaries,
      ArrayPrototypeToSorted(dictionaries[i], compareMembers),
    );
  }

  return function(jsDict, options = kEmptyObject) {
    // Step 1: reject non-object, non-null, non-undefined values.
    if (jsDict != null && type(jsDict) !== 'Object') {
      throw makeException(
        'cannot be converted to a dictionary',
        options,
      );
    }

    // Step 2: create the IDL dictionary value.
    const idlDict = { __proto__: null };

    // Steps 3-4: iterate each dictionary level, then its sorted members.
    for (let i = 0; i < sortedDictionaries.length; i++) {
      const sortedMembers = sortedDictionaries[i];
      for (let j = 0; j < sortedMembers.length; j++) {
        const member = sortedMembers[j];
        // Step 4.1.1: get the dictionary member identifier.
        const key = member.key;
        // Steps 4.1.2-4.1.3: read the JavaScript member value.
        const jsMemberValue = jsDict == null ? undefined : jsDict[key];

        // Step 4.1.4: convert and store present member values.
        if (jsMemberValue !== undefined) {
          const converter = member.converter;
          // Step 4.1.4.1: convert the JavaScript value to IDL.
          const idlMemberValue = converter(
            jsMemberValue,
            makeOptions(options, dictionaryMemberContext(key, options)),
          );
          // Validators are a Node.js extension after conversion. They let
          // consumers reject known unsupported values while dictionary
          // conversion still has precise member context. Web Crypto uses this
          // so SubtleCrypto.supports() can make accurate decisions from