This is a built-in CLI process used to retrieve final config objects in various formats OR initialize a single/environment configuration.

  • Alias: c


mhy is able to generate your config files for your environment. Use it to initialize your environment in your IDE/Editor.

mhy config

By default mhy won't overwrite your existing configuration files, it gives you a warning instead. In case you want to overwrite anyway, use the -o --overwrite flag.

mhy config -o

Use the -i --init flag to initialize a single configuration file only.

mhy config webpack -i
# in case you also wan't to overwrite
mhy config webpack -io


In certain situations you might want to initialize only a certain configuration or just want to check the final object mhy will use.

Log out a single config object:

mhy config webpack

You may use the -f --format flag to change the output format:

mhy config webpack -f json

You might want to write the contents into a file, you just need to use the > operator which works both on Windows and Linux:

mhy config webpack --format=mjs > webpack.config.mjs

Available formats:

  • js plain JavaScript object module.exports = module.exports.default = {}

  • mjs plain JavaScript object export default {}

  • json plain JSON object

  • raw try to print out as is


Setting configuration values can be done in multiple ways. Before showing those, let's get famimilar with the configuration loading flow and some definitions first.


  • root entities are being loaded always

  • env entities are being loaded if the current environment matches

Directory structure

This is an example of webpack's structure:

|- root
|- development
|- production
|- index.js

mhy will recursively load all configuration values from the directory structure recursively.

File names are becoming keys in the final object and folders are becoming arrays.


|- root
|- plugins
|- babel.js // returns {foo: 'bar'}
|- resolve.js // returns 'Resolve value'
|- development
|- production

From the directory structure above you will end up having the following object:

plugins: [{ foo: 'bar' }],
resolve: 'Resolve value'

For further examples check out mhy's repository.


  1. Load root from mhy

  2. Load root from local

  3. Load root from package.json

  4. Load env from mhy

  5. Load env from local

  6. Load env from package.json


mhy's practice to to keep every configuration in the package.json of the project. You can manipulate almost every aspect of a configariation object through JSON, even removals, appends, replaces, pushes or even searching and running JavaScript code.

All mhy related values are being stored under the key "mhy" in your package.json. The structure is the same. By default your object basically are being deep merged.

mhy is coming with support for json-merger which enables manipulation of JSON data easily without using JavaScript.

Let's assume the same webpack directory structure as above and the follwing in out package.json file:

"mhy": {
"webpack": {
"development": {
"resolve": "new resolve value",
"plugins": [{
"$append": "kex"

The result for webpack will be:

resolve: "new resolve value",
plugins: [{ foo: 'bar' }, 'kex']

Using files

This method is for more advanced cases or those who prefer to manage their configs in files.

mhy will search a .mhy directory in your project root. There you need to have a config directory with the same environment base as in the previous examples:

|- configs
|- webpack
|- development
|- resolve.js

In your files you need to default export a function that is returning the value. In the first parameter you'll also get the current value of the key if there's any.

module.exports = current => {
return current

Please note that there will be no code transformations applied to your custom config files. Only use syntax/features that are available in your current NodeJS version.

Local processes/commands

Using this method you can have your own, local processes/commands as well. More info on this is about to come, stay tuned!