iter-tools-es/impls/$reduce/reduce.js

The iterable toolbox

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

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

function __reduce(iterable, reducer, initial = undefined) {
  let c = 0;
  let result = initial;

  const peekr = __peekerate(iterable);

  try {
    if (initial === undefined) {
      if (peekr.done) {
        throw new Error('Cannot reduce: no initial value specified and iterable was empty');
      }

      result = peekr.value;
      peekr.advance();
      c = 1;
    }

    while (!peekr.done) {
      result = reducer(result, peekr.value, c++);
      peekr.advance();
    }

    return result;
  } finally {
    peekr.return();
  }
}

exports.__reduce = __reduce;
const reduce = /*#__PURE__*/iterableCurry(__reduce, {
  reduces: true,
  minArgs: 1,
  maxArgs: 2
});
exports.reduce = reduce;