JSON structural diff

Does exactly what you think it does:

Installation

npm install -g json-diff

Contribution policy

1. This project is maintained thanks to your contributions! Please send pull requests.

2. I will merge any pull request that adds something useful, does not break existing things, has reasonable code quality and provides/updates tests where appropriate.

3. Anyone who gets a significant pull request merged gets commit access to the repository.

Usage

Simple:

json-diff a.json b.json

Detailed:

% json-diff --help

Usage: json-diff [-vCjfk] first.json second.json

Arguments:
<first.json>          Old file
<second.json>         New file

General options:
-v, --verbose         Output progress info
-C, --[no-]color      Colored output
-j, --raw-json        Display raw JSON encoding of the diff
-f, --full            Include the equal sections of the document, not just the deltas
-k, --keys-only       Compare only the keys, ignore the differences in values
-h, --help            Display this usage information

In javascript (ES5):

var jsonDiff = require('json-diff')

console.log(jsonDiff.diffString({ foo: 'bar' }, { foo: 'baz' }));
// Output:
//  {
// -  foo: "bar"
// +  foo: "baz"
//  }

// As above, but without console colors
console.log(jsonDiff.diffString({ foo: 'bar' }, { foo: 'baz' }, {color:false}));

// Raw output:
console.log(jsonDiff.diff({ foo: 'bar', b:3}, { foo: 'baz', b:3}));
// Output:
// { foo: { __old: 'bar', __new: 'baz' } }

// Passing in the "full" option:
console.log(jsonDiff.diff({ foo: 'bar', b:3}, { foo: 'baz', b:3}, {full:true}));
// Output:
// { foo: { __old: 'bar', __new: 'baz' }, b: 3 }

In javascript (ES6+):

import { diffString, diff } from 'json-diff';

console.log(diffString({ foo: 'bar' }, { foo: 'baz' }));
console.log(diff({ foo: 'bar' }, { foo: 'baz' }));

Features

• colorized, diff-like output
• fuzzy matching of modified array elements (when array elements are object hierarchies)
• "keysOnly" option to compare only the json structure (keys), ignoring the values
• "full" option to output the entire json tree, not just the deltas
• reasonable test coverage (far from 100%, though)

Output Language in Raw-json mode ("full" mode)

ARRAYS

Unless two arrays are equal, all array elements are transformed into 2-tuple arrays:

• The first element is a one character string denoting the equality ('+', '-', '~', ' ')
• The second element is the old (-), new (+), altered sub-object (~), or unchanged (' ') value
  json-diff.js --full --raw-json <(echo '[1,7,3]') <(echo '[1,2,3]') [ [ " ", 1 ], [ "-", 7 ], [ "+", 2 ], [ " ", 3 ] ] json-diff.js --full --raw-json <(echo '[1,["a","b"],4]') <(echo '[1,["a","c"],4]') [ [ " ", 1 ], [ "~", [ [ " ", "a" ], [ "-", "b" ], [ "+", "c" ] ] ], [ " ", 4 ] ]
• If two arrays are equal, they are left as is.

OBJECTS

Object property values:

• If equal, they are left as is

• Unequal scalar values are replaced by an object containing the old and new value:

  json-diff.js --full --raw-json <(echo '{"a":4}') <(echo '{"a":5}') { "a": { "__old": 4, "__new": 5 } }

• Unequal arrays and objects are replaced by their diff:

  json-diff.js --full --raw-json <(echo '{"a":[4,5]}') <(echo '{"a":[4,6]}') { "a": [ [ " ", 4 ], [ "-", 5 ], [ "+", 6 ] ] }

Object property keys:

• Object keys that are deleted or added between two objects are marked as such:
  json-diff.js --full --raw-json <(echo '{"a":[4,5]}') <(echo '{"b":[4,5]}') { "a__deleted": [ 4, 5 ], "b__added": [ 4, 5 ] } json-diff.js --full --raw-json <(echo '{"a":[4,5]}') <(echo '{"b":[4,6]}') { "a__deleted": [ 4, 5 ], "b__added": [ 4, 6 ] }

Non-full mode

• In regular, delta-only (non-"full") mode, equal properties and values are omitted:

  json-diff.js --raw-json <(echo '{"a":4, "b":6}') <(echo '{"a":5,"b":6}') { "a": { "__old": 4, "__new": 5 } }

• Equal array elements are represented by a one-tuple containing only a space " ":

  json-diff.js --raw-json <(echo '[1,7,3]') <(echo '[1,2,3]') [ [ " " ], [ "-", 7 ], [ "+", 2 ], [ " " ] ]

Tests

Run:

npm test

Output:

json-diff@0.5.3 test
coffee -c test; mocha test/*.js

colorizeToArray
    ✔ should return ' <value>' for a scalar value
    ✔ should return ' <value>' for 'null' value
    ✔ should return ' <value>' for 'false' value
    ✔ should return '-<old value>', '+<new value>' for a scalar diff
    ✔ should return '-<old value>', '+<new value>' for 'null' and 'false' diff
    ✔ should return '-<removed key>: <removed value>' for an object diff with a removed key
    ✔ should return '+<added key>: <added value>' for an object diff with an added key
    ✔ should return '+<added key>: <added value>' for an object diff with an added key with 'null' value
    ✔ should return '+<added key>: <added value>' for an object diff with an added key with 'false' value
    ✔ should return '+<added key>: <added stringified value>' for an object diff with an added key and a non-scalar value
    ✔ should return ' <modified key>: <colorized diff>' for an object diff with a modified key
    ✔ should return '+<inserted item>' for an array diff
    ✔ should return '-<deleted item>' for an array diff
    ✔ should handle an array diff with subobject diff

colorize
    ✔ should return a string with ANSI escapes
    ✔ should return a string without ANSI escapes on { color: false }

diff
    with simple scalar values
    ✔ should return undefined for two identical numbers
    ✔ should return undefined for two identical strings
    ✔ should return { __old: <old value>, __new: <new value> } object for two different numbers
    with objects
    ✔ should return undefined for two empty objects
    ✔ should return undefined for two objects with identical contents
    ✔ should return undefined for two object hierarchies with identical contents
    ✔ should return { <key>__deleted: <old value> } when the second object is missing a key
    ✔ should return { <key>__added: <new value> } when the first object is missing a key
    ✔ should return { <key>: { __old: <old value>, __new: <new value> } } for two objects with different scalar values for a key
    ✔ should return { <key>: <diff> } with a recursive diff for two objects with different values for a key
    with arrays of scalars
    ✔ should return undefined for two arrays with identical contents
    ✔ should return [..., ['-', <removed item>], ...] for two arrays when the second array is missing a value
    ✔ should return [..., ['+', <added item>], ...] for two arrays when the second one has an extra value
    ✔ should return [..., ['+', <added item>]] for two arrays when the second one has an extra value at the end (edge case test)
    with arrays of objects
    ✔ should return undefined for two arrays with identical contents
    ✔ should return undefined for two arrays with identical, empty object contents
    ✔ should return undefined for two arrays with identical, empty array contents
    ✔ should return undefined for two arrays with identical array contents including 'null'
    ✔ should return undefined for two arrays with identical, repeated contents
    ✔ should return [..., ['-', <removed item>], ...] for two arrays when the second array is missing a value
    ✔ should return [..., ['+', <added item>], ...] for two arrays when the second array has an extra value
    ✔ should return [['+', <added item>], ..., ['+', <added item>]] for two arrays containing objects of 3 or more properties when the second array has extra values (fixes issue #57)
    ✔ should return [..., ['+', <added item>], ...] for two arrays when the second array has a new but nearly identical object added
    ✔ should return [..., ['~', <diff>], ...] for two arrays when an item has been modified

diff({full: true})
    with simple scalar values
    ✔ should return the number for two identical numbers
    ✔ should return the string for two identical strings
    ✔ should return { __old: <old value>, __new: <new value> } object for two different numbers
    with objects
    ✔ should return an empty object for two empty objects
    ✔ should return the object for two objects with identical contents
    ✔ should return the object for two object hierarchies with identical contents
    ✔ should return { <key>__deleted: <old value>, <remaining properties>} when the second object is missing a key
    ✔ should return { <key>__added: <new value>, <remaining properties> } when the first object is missing a key
    ✔ should return { <key>: { __old: <old value>, __new: <new value> } } for two objects with different scalar values for a key
    ✔ should return { <key>: <diff>, <equal properties> } with a recursive diff for two objects with different values for a key
    ✔ should return { <key>: <diff>, <equal properties> } with a recursive diff for two objects with different values for a key
    with arrays of scalars
    ✔ should return an array showing no changes for any element for two arrays with identical contents
    ✔ should return [[' ', <unchanged item>], ['-', <removed item>], [' ', <unchanged item>]] for two arrays when the second array is missing a value
    ✔ should return [' ', <unchanged item>], ['+', <added item>], [' ', <unchanged item>]] for two arrays when the second one has an extra value
    ✔ should return [' ', <unchanged item>s], ['+', <added item>]] for two arrays when the second one has an extra value at the end (edge case test)
    with arrays of objects
    ✔ should return an array of unchanged elements for two arrays with identical contents
    ✔ should return an array with an unchanged element for two arrays with identical, empty object contents
    ✔ should return an array with an unchanged element for two arrays with identical, empty array contents
    ✔ should return an array of unchanged elements for two arrays with identical array contents including 'null'
    ✔ should return an array of unchanged elements for two arrays with identical, repeated contents
    ✔ should return [[' ', <unchanged item>], ['-', <removed item>], [' ', <unchanged item>]] for two arrays when the second array is missing a value
    ✔ should return [[' ', <unchanged item>], ['+', <added item>], [' ', <unchanged item>]] for two arrays when the second array has an extra value
    ✔ should return [[' ', <unchanged item>], ['+', <added item>], [' ', <unchanged item>]] for two arrays when the second array has a new but nearly identical object added
    ✔ should return [[' ', <unchanged item>], ['~', <diff>], [' ', <unchanged item>]] for two arrays when an item has been modified

diff({keysOnly: true})
    with simple scalar values
    ✔ should return undefined for two identical numbers
    ✔ should return undefined for two identical strings
    ✔ should return undefined object for two different numbers
    with objects
    ✔ should return undefined for two empty objects
    ✔ should return undefined for two objects with identical contents
    ✔ should return undefined for two object hierarchies with identical contents
    ✔ should return { <key>__deleted: <old value> } when the second object is missing a key
    ✔ should return { <key>__added: <new value> } when the first object is missing a key
    ✔ should return undefined for two objects with different scalar values for a key
    ✔ should return undefined with a recursive diff for two objects with different values for a key
    ✔ should return { <key>: <diff> } with a recursive diff when second object is missing a key and two objects with different values for a key
    with arrays of scalars
    ✔ should return undefined for two arrays with identical contents
    ✔ should return undefined for two arrays with when an item has been modified
    ✔ should return [..., ['-', <removed item>], ...] for two arrays when the second array is missing a value
    ✔ should return [..., ['+', <added item>], ...] for two arrays when the second one has an extra value
    ✔ should return [..., ['+', <added item>]] for two arrays when the second one has an extra value at the end (edge case test)
    with arrays of objects
    ✔ should return undefined for two arrays with identical contents
    ✔ should return undefined for two arrays with identical, empty object contents
    ✔ should return undefined for two arrays with identical, empty array contents
    ✔ should return undefined for two arrays with identical, repeated contents
    ✔ should return [..., ['-', <removed item>], ...] for two arrays when the second array is missing a value
    ✔ should return [..., ['+', <added item>], ...] for two arrays when the second array has an extra value
    ✔ should return [..., ['~', <diff>], ...] for two arrays when an item has been modified

diffString
    ✔ should produce the expected result for the example JSON files
    ✔ should produce the expected colored result for the example JSON files
    ✔ return an empty string when no diff found


90 passing (42ms)

Change Log

• 0.6.2 Provide examples of setting mode from code.
• 0.6.1 Return exit code 0. Update cli-color to the latest version.
• 0.6.0 Convert project code to ES6
• 0.5.5 Fix bug in scalarize fuzzy compare logic
• 0.4.0 Add --keys-only feature

License

© Andrey Tarantsov. Distributed under the MIT license.