_isIndex.js

/** Used as references for various `Number` constants. */
var MAX_SAFE_INTEGER = 9007199254740991;

/** Used to detect unsigned integer values. */
var reIsUint = /^(?:0|[1-9]\d*)$/;

/**
 * Checks if `value` is a valid array-like index.
 *
 * @private
 * @param {*} value The value to check.
 * @param {number} [length=MAX_SAFE_INTEGER] The upper bounds of a valid index.
 * @returns {boolean} Returns `true` if `value` is a valid index, else `false`.
 */
function isIndex(value, length) {
  var type = typeof value;
  length = length == null ? MAX_SAFE_INTEGER : length;

  return !!length &&
    (type == 'number' ||
      (type != 'symbol' && reIsUint.test(value))) &&
        (value > -1 && value % 1 == 0 && value < length);
}

module.exports = isIndex;