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    2.0.1 • Public • Published

    Merge json files

    Merge Json files using this webpack plugin.

    For example,it will be useful to merge i18n json files which are in different modules into a single final json files in angular2 or react modules.

    Latest version and breaking changes.

    • Breaking changes introduced in latest version 2.0.0, now all values will be overwritten including arrays, earlier behaviour was to concatenate array and overrite literals.Going foward to concatenate either literals or arrays, pass overwrite false as an input, this will concatenate all values in target with source values.

    • This version also fixes compatibility issue with Webpack 5


    Install with npm

    npm i merge-jsons-webpack-plugin
    var MergeJsonWebpackPlugin = require("merge-jsons-webpack-plugin");
    new MergeJsonWebpackPlugin({
        files: ["./jsons/file1.json", "./jsons/file3.json", "./jsons/file2.json"],
        output: {
            fileName: "./dist/result.json",


    You can specify either files or groupBy under output.

    1) By files
    If you want to merge group of files use like this.

    new MergeJsonWebpackPlugin({
        debug: true,
        files: ["./jsons/file1.json", "./jsons/file3.json", "./jsons/file2.json"],
        output: {
            fileName: "./dist/result.json",
    Field Name Description
    files Array of json files to be merged
    output.fileName Name of merged output file ,relative path from output.path entry

    2) By Patterns
    This plugin uses glob for searching file patterns,please refer glob for usage for sample pattern. You can specify a pattern to pull all the files that satify the particular pattern and output a single json file.

    new MergeJsonWebpackPlugin({
        encoding: "ascii",
        debug: true,
        output: {
            groupBy: [
                    pattern: "{./jsons/module*/en.json,./jsons/file1.json}",
                    fileName: "./dist/en.json",
                    pattern: "{./jsons/module*/es.json,./jsons/file2.json}",
                    fileName: "./dist/es.json",
        globOptions: {
            nosort: true,
    groupBy Array of patterns and corresponding fileNames.
    groupBy[].pattern Pattern to search files for. eg: **/en.json will pull all en.json files under current working directory and sub directories
    Do not use curly brackets if there is only single pattern to consider pattern:"./node_modules/**/en.json"
    Use curly brackets to group more than one pattern together pattern:"{./node_modules/**/en.json,./src/assets/i18n/en.json}"
    groupBy[].fileName output file name for the corresponding pattern.Relative path from output.path entry

    3) Run time files

    Files generated at run time can also be specified as input to the pattern.The plugin will lookup in the compilation.assets of webpack and try to load it for processing.


    key Description.
    debug if true, logs will be enabled, by default debug is false.
    encoding Optional, encoding to be used default is utf-8.
    globOptions Optional, glob options to change pattern matching behavior.
    prefixFileName Optional. If true, file names will be prefixed to each file content and merged with outfile

    By default, the generated prefix is ​​simply the filename without the .json extension. If you want to customize the process of generating prefixes, you can pass a function as this option. The function should take exactly one argument (the file path) and returns the prefix.
    space Optional. A String or Number object that's used to insert white space into the output JSON file for readability purposes. See space parameter description on MDN for details.
    duplicates Default value is false.If true, keys at same heirarchy will be preserved in an array, check example.
    overwrite Default true, if false values(for same keys) at same heirarchy will be preserved in an array. Check example, issue #31, issue #63 .

    Change Logs

    Version Changes
    1.0.8 Error handling improved. Now fileName is relative path to output path specified
    1.0.10 File watching feature added, result will be automatically refreshed if json files are modified
    1.0.11 Publish issues with previous version
    1.0.12 Added glob options handling
    1.0.13 When using groupBy,fixed issue of compilation more than once, added capability to read dynamically generated files,and conditional logging
    1.0.14 Webpack 4 breaking changes fix
    1.0.15 prefixFileName option added, for feature request #31
    1.0.16 Webpack 4 compatibile api changes
    1.0.17 Filex extension check removed,file can be of any extention as long as content is json.Testcases also added
    1.0.18 Bom issue fix #22
    1.0.19 Support for custom "prefixFileName" function
    1.0.20 Output formatting via space parameter added, preserving duplicates in an array if duplicates:true instead of overriding existing value.
    2.0.0-alpha Breaking Changes Webpack 5 compatibility update, removed duplicates option, instead added overwrite with default value true, this will break existing behaviour of concatination in case of an array, instead now by default overwrites array value in target object.
    2.0.0 Json processing moved to compilation hook additionalAssets and changed to sync to fix issue #68


    To see sample you can navigate to example folder. From the root folder merge-jsons-webpack-plugin, you can start the sample application as mentioned below

       > npm install
       > npm start

    Access the web application at




    npm i merge-jsons-webpack-plugin

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