numeric-range-iterator.js

'use strict';
var global = require('../internals/global');
var InternalStateModule = require('../internals/internal-state');
var createIteratorConstructor = require('../internals/create-iterator-constructor');
var isObject = require('../internals/is-object');
var defineProperties = require('../internals/object-define-properties').f;
var DESCRIPTORS = require('../internals/descriptors');

var INCORRECT_RANGE = 'Incorrect Number.range arguments';
var NUMERIC_RANGE_ITERATOR = 'NumericRangeIterator';

var setInternalState = InternalStateModule.set;
var getInternalState = InternalStateModule.getterFor(NUMERIC_RANGE_ITERATOR);

var RangeError = global.RangeError;
var TypeError = global.TypeError;

var $RangeIterator = createIteratorConstructor(function NumericRangeIterator(start, end, option, type, zero, one) {
  if (typeof start != type || (end !== Infinity && end !== -Infinity && typeof end != type)) {
    throw new TypeError(INCORRECT_RANGE);
  }
  if (start === Infinity || start === -Infinity) {
    throw new RangeError(INCORRECT_RANGE);
  }
  var ifIncrease = end > start;
  var inclusiveEnd = false;
  var step;
  if (option === undefined) {
    step = undefined;
  } else if (isObject(option)) {
    step = option.step;
    inclusiveEnd = !!option.inclusive;
  } else if (typeof option == type) {
    step = option;
  } else {
    throw new TypeError(INCORRECT_RANGE);
  }
  if (step == null) {
    step = ifIncrease ? one : -one;
  }
  if (typeof step != type) {
    throw new TypeError(INCORRECT_RANGE);
  }
  if (step === Infinity || step === -Infinity || (step === zero && start !== end)) {
    throw new RangeError(INCORRECT_RANGE);
  }
  // eslint-disable-next-line no-self-compare -- NaN check
  var hitsEnd = start != start || end != end || step != step || (end > start) !== (step > zero);
  setInternalState(this, {
    type: NUMERIC_RANGE_ITERATOR,
    start: start,
    end: end,
    step: step,
    inclusiveEnd: inclusiveEnd,
    hitsEnd: hitsEnd,
    currentCount: zero,
    zero: zero
  });
  if (!DESCRIPTORS) {
    this.start = start;
    this.end = end;
    this.step = step;
    this.inclusive = inclusiveEnd;
  }
}, NUMERIC_RANGE_ITERATOR, function next() {
  var state = getInternalState(this);
  if (state.hitsEnd) return { value: undefined, done: true };
  var start = state.start;
  var end = state.end;
  var step = state.step;
  var currentYieldingValue = start + (step * state.currentCount++);
  if (currentYieldingValue === end) state.hitsEnd = true;
  var inclusiveEnd = state.inclusiveEnd;
  var endCondition;
  if (end > start) {
    endCondition = inclusiveEnd ? currentYieldingValue > end : currentYieldingValue >= end;
  } else {
    endCondition = inclusiveEnd ? end > currentYieldingValue : end >= currentYieldingValue;
  }
  if (endCondition) {
    return { value: undefined, done: state.hitsEnd = true };
  } return { value: currentYieldingValue, done: false };
});

var getter = function (fn) {
  return { get: fn, set: function () { /* empty */ }, configurable: true, enumerable: false };
};

if (DESCRIPTORS) {
  defineProperties($RangeIterator.prototype, {
    start: getter(function () {
      return getInternalState(this).start;
    }),
    end: getter(function () {
      return getInternalState(this).end;
    }),
    inclusive: getter(function () {
      return getInternalState(this).inclusiveEnd;
    }),
    step: getter(function () {
      return getInternalState(this).step;
    })
  });
}

module.exports = $RangeIterator;