Convert various time formats to milliseconds at build time in Babel.

Simply install and configure babel-plugin-macros and then use ms.macro the same way you use ms.

Given the following input:

import ms from 'ms.macro';

const ONE_DAY = ms('1 day');
const TWO_DAYS = ms('2 days');

Babel will produce the following output:

const ONE_DAY = 86400000;
const TWO_DAYS = 172800000;

It also works as a tagged template literal:

const ONE_DAY = ms`1 day`;
const TWO_DAYS = ms`2 days`;

That will produce the same output as the function version.

The two main advantages of running ms as a macro are that there are no runtime dependencies and any errors (such as mistakenly callingms('1 da') instead of ms('1 day')) become build-time errors rather than run-time errors.

This macro only supports the single string-argument signature of ms, i.e., passing a single string and getting back a number. This is because when you are converting a number of milliseconds to an equivalent string representation you are typically using calculated values not available at build-time. If you want to convert a number of milliseconds to an equivalent string representation you should use the ms package directly. If you want to use both packages together, you can give the imported values different names:

import ms from 'ms';
import msm from './ms.macro';

const ONE_DAY = msm('1 day');
const str = ms(172800000);

That will result in the following output:

import ms from 'ms';

const ONE_DAY = 86400000;
const str = ms(172800000);

MIT