Registry / devops / merge-json-webpack-plugin

merge-json-webpack-plugin

library6.2.1jsnpmunverified

Webpack 5 plugin that merges multiple JSON files into a single output file during the build process. Version 6.2.1 is current, with a stable release cadence. Supports glob patterns for file selection, custom merge functions, optional output minification, and transformation hooks. Differentiates from simple file concatenation by performing deep merge with customizable merge strategy, and integrates directly as a webpack plugin. Requires webpack ^5.0.0 and Node >=12.20.0. Ships TypeScript definitions.

devops

npm install merge-json-webpack-plugin

github ↗package ↗

INSTALL

IMPORT

SIG · MERGE-JSON-WEBPACK

merge-json-webpack-plugin

devopsjavascriptv6.2.1

Install

—

Import

—

Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

MergeJsonPlugin

✓ const MergeJsonPlugin = require('merge-json-webpack-plugin');

✗ import MergeJsonPlugin from 'merge-json-webpack-plugin';

The package does not export ESM; use CommonJS require in webpack config. Alternatively, if using ES modules for webpack config, use dynamic import: const MergeJsonPlugin = (await import('merge-json-webpack-plugin')).default;

type MergeJsonPluginOptions

✓ import type { MergeJsonPluginOptions } from 'merge-json-webpack-plugin';

TypeScript users can import the options type directly; the package provides bundled types.

MergeJsonPlugin (default import with type assertion)

✓ const MergeJsonPlugin = require('merge-json-webpack-plugin');

✗ import MergeJsonPlugin = require('merge-json-webpack-plugin');

In TypeScript, avoid the import = require syntax; use ordinary require with @types/node or a simple const declaration.

Basic webpack config that merges common.json and overrides.json into manifest.json, with optional version injection and minification.

// webpack.config.js const MergeJsonPlugin = require('merge-json-webpack-plugin'); const path = require('path'); module.exports = { plugins: [ new MergeJsonPlugin({ groups: [ { files: ['common.json', 'overrides.json'], to: 'manifest.json', transform: (merged) => { merged.version = process.env.APP_VERSION || '1.0.0'; return merged; }, }, ], minify: process.env.NODE_ENV === 'production', }), ], };

Debug

Known issues

breakingv5.0.0 dropped support for webpack 4 and Node <12.

fix

Upgrade to webpack 5 and Node >=12.

affects: >=5.0.0

breakingv4.0.0 renamed from 'merge-json-webpack-plugin' (npm scoping change) but package name remained same; the plugin constructor changed from 'MergeJsonWebpackPlugin' to 'MergeJsonPlugin'.

fix

Use 'MergeJsonPlugin' instead of 'MergeJsonWebpackPlugin'.

affects: >=4.0.0

deprecatedThe 'cwd' option may be deprecated in future; use webpack context instead.

fix

Use webpack's context option instead of passing cwd to the plugin.

affects: <7.0.0

gotchaWhen using 'pattern' option, the order of merged JSONs is not guaranteed; subsequent files may overwrite earlier ones arbitrarily.

fix

Use 'files' array instead, or ensure your transform/merge function handles order.

affects: *

gotchaThe 'transform' function must return a JSON-serializable object; returning a non-serializable value (e.g., undefined) will cause the output to be empty or malformed.

fix

Ensure transform always returns an object or null; if returning a promise, it must resolve to a valid object.

affects: *

gotchaUsing 'mergeFn' incorrectly can cause performance issues or infinite loops; custom merge functions are called recursively.

fix

Avoid mutating objects inside mergeFn; always return a new object.

affects: *

Errors

Common errors & fixes

Error: Cannot find module 'merge-json-webpack-plugin'

Missing installation or incorrect import path.

fix

Run `npm install -D merge-json-webpack-plugin`.

TypeError: MergeJsonPlugin is not a constructor

Importing the module incorrectly (e.g., default import vs named import).

fix

Use `const MergeJsonPlugin = require('merge-json-webpack-plugin');`.

ValidationError: Invalid configuration object. Webpack has been initialized using a configuration object that does not match the API schema.

Webpack version mismatch; plugin requires webpack 5.

fix

Update webpack to version 5: `npm install -D webpack@5`.

Error: ENOENT: no such file or directory, open 'path/to/file.json'

One of the source files specified in 'files' does not exist.

fix

Check that all file paths are correct and relative to webpack context or the plugin's cwd.

Upgrade

Version history

6.2.1latest on npm

Audit

Dependencies

webpackrequiredpeer dependency; plugin only works with webpack 5+

fast-globoptionalused for pattern matching when 'pattern' option is specified

Agent activity

2 hits · last 30 days

node

Resources

githubhttps://github.com/sibiraj-s/merge-json-webpack-plugin ↗

packagehttps://www.npmjs.com/package/merge-json-webpack-plugin ↗