const occurrenceMap = arr => arr.reduce((acc, current) => (acc[current] = (acc[current] || 0) + 1, acc), {});
Returns an object where the keys are the array entries and the values the number of their occurrences.
The repository & npm package
You can find the all the utility functions from this series at github.com/martinkr/onelinecode
The library is also published to npm as @onelinecode for your convenience.
The code and the npm package will be updated every time I publish a new article.
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Top comments (2)
You could use destructuring and nullish coalescing:
Cheers!
Thank you for sharing! Yes, there are multiple other ways to achieve this task in javascript. As so often in programming, at one point you have to choose ;)
I checked the benchmarks and for me the alternative you provided is much slower (
11,688 ops/secvs.7.81 ops/secon jsbench). But of course there can be different performance results depending on the engine and environment as well as other factors for the decision which way to go.Cheers!