fast-deep-equal
Fast deep equal
About
Fast deep equal
Live mirror of the GitHub README. Updated whenever the repo's default branch changes.
fast-deep-equal
The fastest deep equal with ES6 Map, Set and Typed arrays support.
Install
npm install fast-deep-equal
Features
- ES5 compatible
- works in node.js (8+) and browsers (IE9+)
- checks equality of Date and RegExp objects by value.
ES6 equal (require('fast-deep-equal/es6')) also supports:
- Maps
- Sets
- Typed arrays
Usage
var equal = require('fast-deep-equal');
console.log(equal({foo: 'bar'}, {foo: 'bar'})); // true
To support ES6 Maps, Sets and Typed arrays equality use:
var equal = require('fast-deep-equal/es6');
console.log(equal(Int16Array([1, 2]), Int16Array([1, 2]))); // true
To use with React (avoiding the traversal of React elements' _owner property that contains circular references and is not needed when comparing the elements - borrowed from react-fast-compare):
var equal = require('fast-deep-equal/react');
var equal = require('fast-deep-equal/es6/react');
Performance benchmark
Node.js v12.6.0:
fast-deep-equal x 261,950 ops/sec ±0.52% (89 runs sampled)
fast-deep-equal/es6 x 212,991 ops/sec ±0.34% (92 runs sampled)
fast-equals x 230,957 ops/sec ±0.83% (85 runs sampled)
nano-equal x 187,995 ops/sec ±0.53% (88 runs sampled)
shallow-equal-fuzzy x 138,302 ops/sec ±0.49% (90 runs sampled)
underscore.isEqual x 74,423 ops/sec ±0.38% (89 runs sampled)
lodash.isEqual x 36,637 ops/sec ±0.72% (90 runs sampled)
deep-equal x 2,310 ops/sec ±0.37% (90 runs sampled)
deep-eql x 35,312 ops/sec ±0.67% (91 runs sampled)
ramda.equals x 12,054 ops/sec ±0.40% (91 runs sampled)
util.isDeepStrictEqual x 46,440 ops/sec ±0.43% (90 runs sampled)
assert.deepStrictEqual x 456 ops/sec ±0.71% (88 runs sampled)
The fastest is fast-deep-equal
To run benchmark (requires node.js 6+):
npm run benchmark
Please note: this benchmark runs against the available test cases. To choose the most performant library for your application, it is recommended to benchmark against your data and to NOT expect this benchmark to reflect the performance difference in your application.
Enterprise support
fast-deep-equal package is a part of Tidelift enterprise subscription - it provides a centralised commercial support to open-source software users, in addition to the support provided by software maintainers.
Security contact
To report a security vulnerability, please use the Tidelift security contact. Tidelift will coordinate the fix and disclosure. Please do NOT report security vulnerability via GitHub issues.
License
Quick facts
npm install fast-deep-equalHow Sourcemap Explorer detects fast-deep-equal
We catch fast-deep-equal from two complementary signals: bundled source paths and the embedded package.json. Modern bundlers (webpack, Vite, esbuild, Rollup, Turbopack) preserve the original node_modules/fast-deep-equal/ paths inside the JavaScript sourcemap's sources[] array — that's the canonical signal. When the matching package.json is also captured in sourcesContent[], we read the exact version field — patch number included. No regex guessing, no version inference.
- 1
Confirm the site exposes sourcemaps
In DevTools Network, check the response headers of any application script for `SourceMap` or `X-SourceMap`. Failing that, fetch the script's last 4 KB and look for a `//# sourceMappingURL=` comment.
- 2
Find the package in the bundle
Open DevTools → Network → reload. Click any application script and look at its sourcemap. Inside, search `sources[]` for entries matching `node_modules/fast-deep-equal/` — every match confirms the package is bundled. The matching `sourcesContent[i]` for `node_modules/fast-deep-equal/package.json` gives you the exact installed version.
- 3
Read the version directly from package.json
Run `jq -r '. as $m | $m.sources | to_entries[] | select(.value | endswith("node_modules/fast-deep-equal/package.json")) | $m.sourcesContent[.key] | fromjson | .version' bundle.js.map`. Sourcemap Explorer automates the same query in the popup.
Recent versions
FAQ
What is fast-deep-equal used for?
Fast deep equal
How can I tell if a website is using fast-deep-equal?
Open the page in Chrome with the Sourcemap Explorer extension installed and read the Stack tab. We catch `fast-deep-equal` from two complementary signals: `node_modules/fast-deep-equal/` paths inside the JavaScript sourcemap, and the embedded `package.json` we read for exact-version detection. Without the extension you can do the same lookup manually in DevTools — the steps are listed in the "How Sourcemap Explorer detects" section above.
What is the latest version of fast-deep-equal?
3.1.3, as published on the npm registry. The "Recent versions" table on this page lists the most recent 8 releases with their release dates. Sourcemap Explorer reports the version actually bundled into a site, which can lag the latest release by months on real-world deployments.
Where can I read more?
Project homepage: https://github.com/epoberezkin/fast-deep-equal#readme. Source code: https://github.com/epoberezkin/fast-deep-equal. Published on npm: https://www.npmjs.com/package/fast-deep-equal. Licensed as MIT.
Detected by Sourcemap Explorer
When a bundle ships sourcemaps, we read the embedded package.json for fast-deep-equal and report the precise version. Without sourcemaps, an import / require in the page's scripts is enough to flag it.