26 lines
1.1 KiB
Markdown
26 lines
1.1 KiB
Markdown
---
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title: 'Using JS Set''s to Find Elements '
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date: 2019-07-09T20:27:09.247Z
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tags:
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- Tech
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description: >-
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JS's `new Set()` can be the new Hash table optimization for reducing nested
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loops. So I've put together a little code snippet to show this in practice.
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---
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Functionally for one check, this is identical to checking the `.indexOf()` or `.includes()` of an Array. However, in cases where you're filtering a large array down to match a list of ID's, for example, the nested looping can result in a performance hit.
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Traditionally hash tables were used for speeding up this search, but with ES2015 we can now leverage Sets which are easier to read and still result in a single loop that's equal to the length of the Array and no more.
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(Can be further optimized by ending when running out of needles)
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```js
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// Example Data
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let hugeArray = [...Array(10000).keys()].map(id => { return {id}; }); // [{id: 0}, ..., {id: 9999}]
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let needles = [1010, 2020, 3030, 4040, 5050, 6060, 7070, 8080, 9090];
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// Finding matching elements
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let needlesSet = new Set(needles);
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let matches = hugeArray.filter(obj => needlesSet.has(obj.id));
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```
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https://gitlab.com/snippets/1873655
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