mcjspacker

mcjspacker

A modern JavaScript-based generator for Minecraft datapack functions. Write Minecraft functions using template literals and JavaScript logic, and output them as .mcfunction files for your datapack. Perfect for automating repetitive tasks, generating dynamic content, and keeping your Minecraft projects DRY and maintainable.

Features

• Write Minecraft functions using JavaScript template literals
• Supports named and anonymous functions
• Output to any directory, ready for use in datapacks
• Compose functions, use variables, and generate code dynamically
• Simple, intuitive API

Quick Setup

Prerequisites

• Node.js v16 or newer

Create a New Project

You can quickly scaffold a new project using npx:

npx mcjspacker <directory> [namespace]
cd <directory>
npm install

• <directory>: The directory to create (relative or absolute path). If it exists and is not empty, the command will abort.
• [namespace] (optional): The namespace to use for the datapack. If omitted, the directory name is used (normalized).

[!NOTE]
This will create a new directory <directory> with example files and all dependencies installed.

[!TIP] It's recommended to pick <directory> as a directory in your world's datapacks directory. for example: %APPDATA%/.minecraft/saves/TestingWorld/datapacks/mypack

Run the Project

To generate your datapack files, use the following commands:

npm run build

This will run your main script (default to src/index.js) and generate the Minecraft function files in the appropriate output directory (e.g., data/<namespace>/function).

npm run watch

This will watch your src/ directory for changes and automatically rebuild your datapack whenever you save a file. This is useful for rapid development and iteration.

After running either command, you should see generated files in the data/ directory, ready to be used as a Minecraft datapack.

Documentation

API

Create context: createMCF({ outputDir, functionCallPrefix })

Initializes the generator.

• outputDir (string): Output directory for generated files.
• functionCallPrefix (string): Prefix for function calls (e.g., 'mydatapack:').

[!WARNING]
Calling this function will delete the directory outputDir and all its contents.

[!WARNING] Do not call this function twice with related outputDir as it will override eachother.

Named function: mcf.functionName`...`

• {outputDir}/function_name.mcfunction.

Subfolders: mcf.folder.functionName`...`

• {outputDir}/folder/function_name.mcfunction.

Anonymous function: mcf`...`

• {outputDir}/anonymous/anonymous_{i}.mcfunction

Anonymous function in a folder: mcf.folder.anonymous`...`

• {outputDir}/folder/anonymous/anonymous_{i}.mcfunction

mcf[dynamicName]`...`

Use dynamic names for functions or folders.

Function call: `${mcf.funcName}` or '' + mcf.funcName

• Converts it into a function call string 'function {functionCallPrefix}func_name'.

[!TIP] mcjspacker will insert : or / after functionCallPrefix if needed

Recommended Usage Style

// ===== mcf.js =====

import { createMCF } from 'mcjspacker';

// if you want to have all functions generated
export const mcf = createMCF({
  outputDir: 'data/mynamespace/function',
  functionCallPrefix: 'mynamespace'
});

// if you want to have the generated functions in a folder
// ⚠️ do NOT call createMCF() with related folders as they will override eachother
export const mcfInAFolder = createMCF({
  outputDir: 'data/mynamespace/function/generated',
  functionCallPrefix: 'mynamespace:generated'
});



// ===== playerKit.js =====

import mcf from "./mcf.js";
const directory = mcf.playerKit;
// declare public functions
export const { giveStarterKit , giveAdvancedKit } = directory;
// declare private functions
const { equipArmor, anonymous: a } = directory;

/*
 * declaring the functions help you refer to them in other functions
 * and being free to order them as you want.
 * 
 * It also automatically names the functions because:
 *   export const {foo, bar} = mcf.dir;
 * is equvalent to:
 *   export const foo = mcf.dir.foo;
 *   export const bar = mcf.dir.bar;
 * 
 */

giveStarterKit`
  ${equipArmor}
  give @s wooden_sword
`;

const xpForGoldApple = 100;
giveAdvancedKit`
  ${equipArmor}
  give @s iron_sword
  execute if score @s experience matches ${xpForGoldApple}.. run ${a`
    give @s golden_apple
  `}
`;

equipArmor`
  item replace entity @s armor.chest with leather_chestplate
  item replace entity @s armor.legs with leather_leggings
  item replace entity @s armor.feet with leather_boots
  item replace entity @s armor.head with leather_helmet
`;

// if you prefer, you can also define something like
const equip = (slot, item) => `item replace entity @s armor.${slot} with ${item}`;
a`
  ${equip('chest', 'leather_chestplate')}
  ${equip('legs', 'leather_leggings')}
  ${equip('feet', 'leather_boots')}
  ${equip('head', 'leather_helmet')}
`;

Dynamic Function Names

const players = ['Steve', 'Alex'];
for (const player of players) {
  mcf[`greet_${player.toLowerCase()}`]`
    say Hello, ${player}!
  `;
}

Advanced: Recursive Functions

const {rec} = mcf.folder;
rec`
  scoreboard players add @s example 1
  say hello
  execute if score @s example matches ..10 run ${rec}
`;

Advanced: Generating Multiple Functions Programmatically

const items = [
  { name: 'platform', model: 'redstone_block' },
  { name: 'slime_block', model: 'slime_block' }
];

// for each item define 'give @s ...'
const functions = items.map(({ name, model }) => mcf[`give_${name}`]`
  give @s item_frame{item_name:'${name}',model:'${model}'}
`);

// call all of the functions
mcf.giveAll`
  ${functions.join('\n')}
`;

Contributing

Contributions are welcome! Please open issues or pull requests for bugs, features, or questions.

License

MIT