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Superfast intersection supporting primitives and objects. Up to 2x to 3x faster than other libraries. In the age of big data, you need it.

Just 990 bytes of ES5 compatible minified code with no dependencies when compressed with CloakedJS. 428 bytes gzipped.

15% faster than the next fastest (lovasoa) for primitve values.

15% faster than the next fastest (fast-array-intersect) for keyed objects.

TWICE the speed of the next fastest (fast-array-intersect) for keyed objects.

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Raw Power Test

Below are node.js v12 benchmarks for v1.1.1 in a 4 core i7 2.86gz Debian 64bit environment intersecting a 100,000 element array with a 50,000 element array having a 50,000 element result.

To run the test in the test/benchmark directory:

node index.js
lodashPrimitive x 64.38 ops/sec ±1.34% (66 runs sampled)
benviePrimitive x 48.18 ops/sec ±4.42% (61 runs sampled)
lovasoaPrimitive x 105 ops/sec ±3.43% (68 runs sampled)
fastArrayIntersect x 71.50 ops/sec ±4.00% (62 runs sampled)
intersectorPrimitive x 121 ops/sec ±3.25% (68 runs sampled)
lodashObject x 46.42 ops/sec ±1.90% (61 runs sampled)
benvieObject x 37.77 ops/sec ±5.91% (50 runs sampled)
fastArrayIntersectObject x 66.50 ops/sec ±4.46% (58 runs sampled)
intersectorObject x 81.58 ops/sec ±3.82% (71 runs sampled)
fastArrayIntersectKeyedObject x 60.94 ops/sec ±2.36% (63 runs sampled)
intersectorKeyedObject x 125 ops/sec ±2.64% (80 runs sampled)

Real World Simulation

In a real world simulation 4 arrays of random length up to 100,000 primitive elements are intersected. The results vary with intersector generally being the fastest but with fast-array-intersect occassionally winning. To run this test in the test/benchmark directory:

node index2.js


The underlying alogrithm is based heavily on the orginal lovaso algorithm. Modern JavaScript constructs such has const have been used so the compiler can do more optimization. Additionally, short circuit continue statements have been used in for loops, which sometimes seems to improve performance. This was a trial and error process.


npm install intersector


Download and use the browser files from the browser directory.


intersector(objectsMixedOrKey) is a function that returns another function configured to do array intersections. It takes one optional argument objectsMixedOrKey. If no value is provided the intersection is optimized for uniform primitive data types across all arrays and will run much faster. If typeof(objectsMixedOrKey)==="string" it is assumed to be a unique key on all objects in the arrays. This will run the second fastest. If objectsMixedOrKey is otherwise not equal to zero, then a Set will be used internally and the algorithm will be slower, although still faster than others. This is useful in the rare cases where there might be mixed primitve types in the target arrays, e.g. [1,2,"2"] and ["1",2,3] which should result in [1,"1",2,"2",3].

The returned intersection function can take any number of arguments.

In NodeJS:

var intersector = require("intersector"),

In browser:

<script src="./browser/intersector.js"></script>

Primitive Intersection

var primitiveIntersect = intersector();
console.log(primitiveIntersect([1,2,3],[3,2])); // [3,2]

Object Intersection

var objectIntersect = intersector(true);
var o1 = {o:1},
	o2 = {o:2},
	o3 = {o:3};
console.log(objectIntersect([o1,o2,o3],[o3,o2])); // [o2,o3];
<script src=""></script>

Updates (reverse chronological order)

2020-11-06 v1.1.0 - Addressed a major bug where intersector was returning incorrect results when provided 3 or more arguments. As a result, inetersector is slightly slower but still the fastest across primitives, keyed objects, and full objects. Added more unit tests and a more realistic benchmark test to avoid this kind of thing in the future!

2020-09-24 v1.0.17 - Added Downrunner documentation support. Improved browser export.

2020-07-15 v1.0.16 - The cat stepped on the keyboard right before a commit and inserted some random stuff (really! ;-) ;-(). Fixed.

2020-07-15 v1.0.15 - Split into three internal functions. Slight speed and size improvement. Speed more consistent across test runs. Easier to maintain. Thanks @titoBouzout!

2020-07-14 v1.0.14 - Documentation updates.

2020-07-13 v1.0.13 - Optimized further for size and speed.

2017-05-29 v1.0.12 - Fixed bug with keyed objects. If a key was undefined on an object, the code would include it.

2017-05-21 v1.0.10 - Minor optimization, moved sort function to be predefined instead of within lexical scope of sort call.

2017-05-21 v1.0.9 - Reverted to var, it is slightly faster. Reduced code size by 50%. Improved performance for objects.

2017-01-15 v1.0.8 - Replaced var with let. Added Codacy quality assessment.

2016-12-29 v1.0.7 - Added option to use unique key which makes object performance better.

2016-12-27 v1.0.6 - Reverted .hasOwnProperty which slowed things down.

2016-12-27 v1.0.5 - Updated benchmark.

2016-12-27 v1.0.4 - Corrected dev package dependencies. Modified code to use .hasOwnProperty.

2016-12-24 v1.0.3 - Exposed a benchmark specification. Updated documentation.

2016-12-24 v1.0.2 - Corrected git repository reference in package.json.

2016-12-23 v1.0.1 - Added lodash intersection to benchmark.

2016-12-21 v1.0.0 - Initial public release.


MIT - see LICENSE file


Superfast intersection supporting primitives and objects. In the age of big data, you need it.







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