Moment: Moment Doesn't work With Jest

Created on 16 Jul 2019 · 9Comments · Source: moment/moment

Describe the bug
When imported into a development setting import moment from 'moment' allows moment to work effectively and does everything I want it to. However when running jest tests that run over the code that calls moment() I get the following error:
"TypeError: moment_1.default is not a function"
Strangely, Importing it in this way: import * as moment from 'moment' allows functionality in test but not in production. I have looked all through jest's issues and this has been a reported issue however the Jest team is confident the issue is on moment's side.

To Reproduce
Steps to reproduce the behaviour:

make a simple function in a react app which calls moment()
add a jest test which will traverse this path.
run the test.
See error

Expected behaviour
Moment should be callable in both test and production in the same way.

Desktop (please complete the following information):

OS: macOS Mojave
Testing: Jest -v 24.8.0

Moment-specific environment
moment -v 2.24.0

Other libraries in use: TypeScript

Please run the following code in your environment and include the output:
console output when moment is imported the way development expects i.e. import moment from 'moment'

console.log src/resources/timestamping.tsx:4
      Tue Jul 16 2019 10:58:16 GMT-0400 (Eastern Daylight Time)
    console.log src/resources/timestamping.tsx:5
      7/16/2019, 10:58:16 AM
    console.log src/resources/timestamping.tsx:6
      240
TypeError: Cannot read property 'version' of undefined.

console output when moment is imported the way it functions in test i.e. import * as moment from 'moment'

console.log src/resources/timestamping.tsx:4
      Tue Jul 16 2019 11:02:46 GMT-0400 (Eastern Daylight Time)
    console.log src/resources/timestamping.tsx:5
      7/16/2019, 11:02:46 AM
    console.log src/resources/timestamping.tsx:6
      240
    console.log src/resources/timestamping.tsx:8
      2.24.0

Documentation Help Wanted

Source

Brendan-Lucas

👍4

Most helpful comment

const moment = require("moment").default || require("moment") is what I came up with, but it only allows use to use moment as a function.
// edit

import * as mom from "moment";
const moment = require("moment").default || require("moment");

Fixes angular / jest problem. But it's still a hack.

KonradLinkowski on 29 Aug 2019

👍2

All 9 comments

const moment = require("moment").default || require("moment") is what I came up with, but it only allows use to use moment as a function.
// edit

import * as mom from "moment";
const moment = require("moment").default || require("moment");

Fixes angular / jest problem. But it's still a hack.

KonradLinkowski on 29 Aug 2019

👍2

blem. But it's still a hack.

Thank you sir, that helped.

brunano21 on 6 Apr 2020

❤1

Is there something the Moment.js side can do here?

marwahaha on 18 May 2020

I was facing this issue when i was using ts-jest for working with typescript and jest. I ended up using babel for typescript support with jest instead and I don't face it anymore. Perhaps the ts-jest library may be doing something under the hood