internal/baseSortedIndexBy.js

/** Used as references for the maximum length and index of an array. */
var MAX_ARRAY_LENGTH = 4294967295,
    MAX_ARRAY_INDEX = MAX_ARRAY_LENGTH - 1;

/* Built-in method references for those with the same name as other `lodash` methods. */
var nativeFloor = Math.floor,
    nativeMin = Math.min;

/**
 * The base implementation of `_.sortedIndexBy` and `_.sortedLastIndexBy`
 * which invokes `iteratee` for `value` and each element of `array` to compute
 * their sort ranking. The iteratee is invoked with one argument; (value).
 *
 * @private
 * @param {Array} array The sorted array to inspect.
 * @param {*} value The value to evaluate.
 * @param {Function} iteratee The iteratee invoked per element.
 * @param {boolean} [retHighest] Specify returning the highest qualified index.
 * @returns {number} Returns the index at which `value` should be inserted into `array`.
 */
function baseSortedIndexBy(array, value, iteratee, retHighest) {
  value = iteratee(value);

  var low = 0,
      high = array ? array.length : 0,
      valIsNaN = value !== value,
      valIsNull = value === null,
      valIsUndef = value === undefined;

  while (low < high) {
    var mid = nativeFloor((low + high) / 2),
        computed = iteratee(array[mid]),
        isDef = computed !== undefined,
        isReflexive = computed === computed;

    if (valIsNaN) {
      var setLow = isReflexive || retHighest;
    } else if (valIsNull) {
      setLow = isReflexive && isDef && (retHighest || computed != null);
    } else if (valIsUndef) {
      setLow = isReflexive && (retHighest || isDef);
    } else if (computed == null) {
      setLow = false;
    } else {
      setLow = retHighest ? (computed <= value) : (computed < value);
    }
    if (setLow) {
      low = mid + 1;
    } else {
      high = mid;
    }
  }
  return nativeMin(high, MAX_ARRAY_INDEX);
}

export default baseSortedIndexBy;