iter-tools-es/impls/$split-groups/split-groups.js

The iterable toolbox

const {
  iterableCurry
} = require('../../internal/iterable.js');

const {
  __spliterateGrouped
} = require('../$spliterate-grouped/spliterate-grouped.js');

const {
  __peekerate
} = require('../$peekerate/peekerate.js');

const initialKey = Symbol('initial group key');

function* groupingSpliterator(split, {
  getKey
}, source) {
  const peekr = __peekerate(source);

  let key = initialKey;
  let idx = 0;

  while (!peekr.done) {
    const lastKey = key;
    key = getKey(peekr.value, idx++);

    if (lastKey !== key) {
      yield split;
      yield key;
    }

    yield peekr.value;
    peekr.advance();
  }
}

function __splitGroups(source, getKey = value => value) {
  return __spliterateGrouped(source, groupingSpliterator, {
    getKey
  });
}

exports.__splitGroups = __splitGroups;
const splitGroups = /*#__PURE__*/iterableCurry(__splitGroups, {
  minArgs: 0,
  maxArgs: 1
});
exports.splitGroups = splitGroups;