Default Loader Plugin

The default loader plugin is responsible for importing migration files written in JavaScript or TypeScript. Migration files can be written using either CommonJS or ES Modules.

Supported extensions

The default loader plugin supports the following extensions:

• .js - either CommonJS or ES Modules depending on your package.json’s type field
• .cjs - CommonJS
• .mjs - ES Modules
• .ts - either CommonJS or ES Modules written in TypeScript
• .cts - CommonJS written in TypeScript
• .mts - ES Modules written in TypeScript

Note

To enable TypeScript support in NodeJS you also need to follow the TypeScript setup guide.

Supported exports

The default loader plugin supports the following exports:

ES Modules

Default export

Exporting a function as the default export.

Async/Await

import { database } from 'some-database';

export default async function someMigration() {
  await database.query(...);
  await database.query(...);
}

Promises

import { database } from 'some-database';

export default function someMigration() {
  // Remember to return the promise
  return database.query(...)
    .then(() => {
      return database.query(...);
    })
}

Callback

import { database } from 'some-database';

export default function someMigration(done) {
  database.query(..., (err) => {
    if (err) {
      return done(err);
    }

    database.query(..., (err) => {
      if (err) {
        return done(err);
      }

      done();
    });
  });
}

Named export

Exporting a function named up.

Async/Await

import { database } from 'some-database';

export const up = async () => {
  await database.query(...);
  await database.query(...);
};

Promises

import { database } from 'some-database';

export const up = () => {
  // Remember to return the promise
  return database.query(...)
    .then(() => {
      return database.query(...);
    })
};

Callback

import { database } from 'some-database';

export const up  = (done) => {
  database.query(..., (err) => {
    if (err) {
      return done(err);
    }

    database.query(..., (err) => {
      if (err) {
        return done(err);
      }

      done();
    });
  });
}

CommonJS

module.exports

Exporting a function as the module.

Async/Await

const { database } = require('some-database');

module.exports = async function someMigration() {
  await database.query(...);
  await database.query(...);
}

Promises

const { database } = require('some-database');

module.exports = function someMigration() {
  // Remember to return the promise
  return database.query(...)
    .then(() => {
      return database.query(...);
    })
}

Callback

const { database } = require('some-database');

module.exports = function someMigration(done) {
  database.query(..., (err) => {
    if (err) {
      return done(err);
    }

    database.query(..., (err) => {
      if (err) {
        return done(err);
      }

      done();
    });
  });
}

exports.up

Exporting an up function.

Async/Await

const { database } = require('some-database');

exports.up = async () => {
  await database.query(...);
  await database.query(...);
};

Promises

const { database } = require('some-database');

exports.up = () => {
  // Remember to return the promise
  return database.query(...)
    .then(() => {
      return database.query(...);
    })
};

Callback

const { database } = require('some-database');

exports.up  = (done) => {
  database.query(..., (err) => {
    if (err) {
      return done(err);
    }

    database.query(..., (err) => {
      if (err) {
        return done(err);
      }

      done();
    });
  });
}