Function groupBy

deps/v8/tools/system-analyzer/helper.mjs:28–50

(array, keyFunction, collect = false)

}

export function groupBy(array, keyFunction, collect = false) {
  if (array.length === 0) return [];
  if (keyFunction === undefined) keyFunction = each => each;
  const keyToGroup = new Map();
  const groups = [];
  const sharedEmptyArray = [];
  let id = 0;
  // This is performance critical, resorting to for-loop
  for (let each of array) {
    const key = keyFunction(each);
    let group = keyToGroup.get(key);
    if (group !== undefined) {
      collect ? group.addEntry(each) : group.add();
      continue;
    }
    let entries = collect ? [each] : sharedEmptyArray;
    group = new Group(key, id++, array.length, entries, 1);
    groups.push(group);
    keyToGroup.set(key, group);
  }
  // Sort by length
  return groups.sort((a, b) => b.length - a.length);
}

export function arrayEquals(left, right, compareFn) {
  if (left == right) return true;