balderdashy/waterline

/**
 * Module dependencies
 */

var lodash4IsSafeInteger = require('lodash.issafeinteger');


/**
 * isSafeNaturalNumber()
 *
 * Determine whether this value is a safe, natural number:
 * • `safe`            | `<= Number.MAX_SAFE_INTEGER`                             (see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER)
 * • `natural`         | `> 0 && !== Infinity && !== NaN && Math.floor(x) === x`  (positive, non-zero, finite, round number.  In other words, no funny business -- aka "positive, non-zero integer")
 * ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 * @param {Ref} value
 * ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 * @returns {Boolean}
 */

module.exports = function isSafeNaturalNumber(value) {

  // Return false for:
  // • NaN
  // • Infinity / -Infinity
  // • 0 / -0
  // • fractions
  // • negative integers
  // • and integers greater than `Number.MAX_SAFE_INTEGER`
  //
  // Otherwise, return true!
  //
  // > For more on `Number.isSafeInteger()`, check out MDN:
  // > https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isSafeInteger

  // Note that, eventually, we can just do:
  // ```
  // return Number.isSafeInteger(value) && value > 0;
  // ```

  // But for compatibility with legacy versions of Node.js, we do:
  // (implementation borrowed from https://github.com/lodash/lodash/blob/4.17.2/lodash.js#L12094)
  return lodash4IsSafeInteger(value) && value > 0;

};