Method observe

lib/internal/perf/observe.js:250–317

(options = kEmptyObject)

  }

  observe(options = kEmptyObject) {
    validateObject(options, 'options');
    const {
      entryTypes,
      type,
      buffered,
    } = { ...options };
    if (entryTypes === undefined && type === undefined)
      throw new ERR_MISSING_ARGS('options.entryTypes', 'options.type');
    if (entryTypes != null && type != null)
      throw new ERR_INVALID_ARG_VALUE('options.entryTypes',
                                      entryTypes,
                                      'options.entryTypes can not set with ' +
                                      'options.type together');

    switch (this.#type) {
      case undefined:
        if (entryTypes !== undefined) this.#type = kTypeMultiple;
        if (type !== undefined) this.#type = kTypeSingle;
        break;
      case kTypeSingle:
        if (entryTypes !== undefined)
          throw lazyDOMException(
            'PerformanceObserver can not change to multiple observations',
            'InvalidModificationError');
        break;
      case kTypeMultiple:
        if (type !== undefined)
          throw lazyDOMException(
            'PerformanceObserver can not change to single observation',
            'InvalidModificationError');
        break;
    }

    if (this.#type === kTypeMultiple) {
      if (!ArrayIsArray(entryTypes)) {
        throw new ERR_INVALID_ARG_TYPE(
          'options.entryTypes',
          'string[]',
          entryTypes);
      }
      maybeDecrementObserverCounts(this.#entryTypes);
      this.#entryTypes.clear();
      for (let n = 0; n < entryTypes.length; n++) {
        if (ArrayPrototypeIncludes(kSupportedEntryTypes, entryTypes[n])) {
          this.#entryTypes.add(entryTypes[n]);
          maybeIncrementObserverCount(entryTypes[n]);
        }
      }
    } else {
      if (!ArrayPrototypeIncludes(kSupportedEntryTypes, type))
        return;
      this.#entryTypes.add(type);
      maybeIncrementObserverCount(type);
      if (buffered) {
        const entries = filterBufferMapByNameAndType(undefined, type);
        SafeArrayPrototypePushApply(this.#buffer, entries);
        kPending.add(this);