index.js

"use strict";

function factory(prng) {

  // Crockford's Base32
  // https://en.wikipedia.org/wiki/Base32
  var ENCODING = "0123456789ABCDEFGHJKMNPQRSTVWXYZ"
  var ENCODING_LEN = ENCODING.length
  var TIME_MAX = 281474976710655
  var TIME_LEN = 10
  var RANDOM_LEN = 16

  function encodeTime(now, len) {
    if (now > TIME_MAX) {
      throw new Error("cannot encode time greater than " + TIME_MAX)
    }
    var mod
    var now
    var str = ""
    for (var x = len; x > 0; x--) {
      mod = now % ENCODING_LEN
      str = ENCODING.charAt(mod) + str
      now = (now - mod) / ENCODING_LEN
    }
    return str
  }

  function encodeRandom(len) {
    var rand
    var str = ""
    for (var x = 0; x < len; x++) {
      rand = Math.floor(ENCODING_LEN * prng())
      str = ENCODING.charAt(rand) + str
    }
    return str
  }

  function ulid() {
    return encodeTime(Date.now(), TIME_LEN) + encodeRandom(RANDOM_LEN)
  }

  ulid.prng = prng
  ulid.encodeTime = encodeTime
  ulid.encodeRandom = encodeRandom

  return ulid

}

/* istanbul ignore next */
function _prng(root) {

  if (root) {
    try {
      return function() {
        return Math.random()
      }
    }
    catch (e) {}
  }
  else {
    try {
      var randomBytes = require("randombytes")
      return function() {
        return randomBytes(2).readUInt16LE() / 0xFFFF
      }
    }
    catch (e) {}
  }

  if (typeof prng !== "function") {
    if (typeof console !== "undefined" && console.warn) {
      console.warn("[ulid] crypto not usable, falling back to insecure Math.random()");
    }
    return function() {
      return Math.random()
    }
  }

}

/* istanbul ignore next */
(function(root, fn) {

  var prng = _prng(root)
  var ulid = fn(prng)

  if (("undefined" !== typeof module) && module.exports) {
    module.exports = ulid
  }
  else if (typeof define === "function" && define.amd) {
    define(function() {
      return ulid
    })
  }
  else {
    root.ulid = ulid
  }

})(typeof window !== "undefined" ? window : null, factory)