Fully or partially merge JSON files via the command line.

npm install jme

Usage

jme file-1.json file-2.json file-3.json > merged.json

file-3.json will be merged with file-2.json and the result will be merged with file-1.json The first file is the target file however, files are never modified, rather the merge result is sent to standard out.

You can pass in any number of files to be merged.

In addition to fully merging json files, you can merge only some of the properties / paths on the JSON object.

Given these files:

// test-1.json
{
  "prop1": {
    "id": 1,
    "tags": [1, 2, 3],
    "level1": {
      "prop1": "t1",
      "customProp1": "t1",
      "level2": { // override this path with the same path from the other files.
        "prop1": "t1",
        "customProp1": "t1"
      }
    }
  }
}


// test-2.json
{
  "prop1": {
    "id": 2,
    "tags": [4, 5, 6],
    "level1": {
      "prop1": "t2",
      "customProp2": "t2",
      "level2": { //merge only this path
        "prop1": "t2",
        "customProp2": "t2"
      }
    }
  }
}

You can choose to merge only a part of the file (in this case prop1.level1.level2)

jme test-1.json test-2.json -p 'prop1.level1.level2'

result:

{
  "prop1": {
    "id": 1,
    "tags": [1, 2, 3],
    "level1": {
      "prop1": "t1",
      "customProp1": "t1",
      "level2": {       //only this path 'prop1.level1.level2' is merged
        "prop1": "t2" // comes from test-2.json
        "customProp2": "t2",// comes from test-2.json
        "customProp1": "t1" // comes from test-1.json
      }
    }
  }
}

You can partially merge multiple paths, just make sure to separate then with comma -p 'prop1.level1.level2,some.other.path,yet.some.other.path'

If the path does not exist in one of the files program will report an error and the merge process will not be executed. However, you can pass an additional flag -u or --allow-undefined to allow undefined paths in the files. In that case, if the path does not exist in the file, that file will be skipped for that particular path.

You can also override the path on the last file target ( -o or --override)

In the next example chosen path will be merged from test-3.json into test-2.json and then that same path will be overridden in test-1.json (no merging with the test-1.json)

Example:

jme test-1.json test-2.json test-3.json --path 'prop1.level1.level2' --override