Function _countGroupLabelsBeforeOption

src/material/core/option/option.ts:300–320

(
  optionIndex: number,
  options: QueryList<MatOption>,
  optionGroups: QueryList<MatOptgroup>,
)

 * @docs-private
 */
export function _countGroupLabelsBeforeOption(
  optionIndex: number,
  options: QueryList<MatOption>,
  optionGroups: QueryList<MatOptgroup>,
): number {
  if (optionGroups.length) {
    let optionsArray = options.toArray();
    let groups = optionGroups.toArray();
    let groupCounter = 0;

    for (let i = 0; i < optionIndex + 1; i++) {
      if (optionsArray[i].group && optionsArray[i].group === groups[groupCounter]) {
        groupCounter++;
      }
    }

    return groupCounter;
  }

  return 0;
}

/**
 * Determines the position to which to scroll a panel in order for an option to be into view.