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    2.0.0-alpha.3 • Public • Published


    Consistent checksum calculation of JSON objects.

    Unit Tests

    Quick start

    const JSum = require('jsum')
    const obj1 = {foo: [{c: 1}, {d: 2, e: 3}], bar: {a: 2, b: undefined}}
    const obj2 = {bar: {b: undefined, a: 2}, foo: [{c: 1}, {e: 3, d: 2}]}
    console.log(JSum.digest(obj1, 'SHA256', 'hex')) // 9a08ad6302b1e9e5682c365c8b24c5ca2ea6db5c90b672bc5b579879136dda0c
    console.log(JSum.digest(obj2, 'SHA256', 'hex')) // 9a08ad6302b1e9e5682c365c8b24c5ca2ea6db5c90b672bc5b579879136dda0c

    Why this module?

    My main goal was to create Etags from JSON objects. The most intuitive approach would have been something like:

    const crypto = require('crypto')
    function checksum (obj) {
      return crypto.createHash('MD5').update(JSON.stringify(myObj)).digest('hex')

    However, this approach would yield two different results for semantically same JSON objects:

    console.log(checksum({"a": 1, "b": 2})) // 608de49a4600dbb5b173492759792e4a
    console.log(checksum({"b": 2, "a": 1})) // 9915965eb40d343a8fe26e4e341d1a05

    JSum on other hand makes sure that semantically same JSON objects always get the same checksum! Moreover, it provides a good deal of time advantage over some other viable modules*:

    Module Time (ms) to hash a 181 MB JSON file (from memory)
    json-hash 81537
    json-stable-stringify 12134
    JSum 7200
    json-checksum FATAL ERROR: [...] - process out of memory

    For this trivial test a huge random JSON file (181 MB) was taken as the base for benchmarking. The listed modules were used to create SHA256 hash of that file. To measure the time, internal console.time(() and console.timeEnd() methods were used. Serious benchmarking is described below.


    You can also run benchmarks to compare performance with similar modules:

    npm i --no-save \
      benchmarked \
      fast-json-stable-stringify \
      json-checksum json-hash \
    node benchmark/index.js


    # benchmark/fixtures/medium.json (77986 bytes)
      fast-json-stable-stringify x 629 ops/sec ±1.67% (81 runs sampled)
      json-checksum x 236 ops/sec ±0.88% (82 runs sampled)
      json-hash x 83.40 ops/sec ±1.25% (60 runs sampled)
      json-stable-stringify x 609 ops/sec ±0.80% (87 runs sampled)
      jsum x 1,118 ops/sec ±0.68% (89 runs sampled)
      fastest is jsum
    # benchmark/fixtures/small.json (456 bytes)
      fast-json-stable-stringify x 67,381 ops/sec ±1.16% (84 runs sampled)
      json-checksum x 21,372 ops/sec ±1.21% (89 runs sampled)
      json-hash x 7,409 ops/sec ±1.17% (75 runs sampled)
      json-stable-stringify x 54,015 ops/sec ±0.89% (83 runs sampled)
      jsum x 90,816 ops/sec ±1.06% (87 runs sampled)
      fastest is jsum


    npm i jsum

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