32 lines
1.6 KiB
Markdown
32 lines
1.6 KiB
Markdown
---
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title: JavaScript's numeric separators explained
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shortTitle: Numeric separators explained
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type: story
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language: javascript
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tags: [math,type]
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author: chalarangelo
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cover: coffee-drip
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excerpt: Numeric separators are a somewhat lesser-known JavaScript syntactic sugar that can make working with large constants a lot easier.
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dateModified: 2021-06-27T05:00:00-04:00
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---
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Numeric separators are a lesser-known JavaScript syntactic sugar that can make working with numeric constants a lot easier. The long and short of it is that you can add underscores (`_`) to numeric values to make them more readable.
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The idea of separating large numeric values with a special character might sound familiar on account of it being a syntax present in multiple other languages, such as Java, Python, Ruby etc. From what I can tell, numeric separators are at their best when creating shared constants that will not change and are very large, have many repeated digits and/or can be ambiguous.
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Apart from readability, numeric separators don't really offer anything else. For the sceptics among us that don't really see a lot of readability value either, I'd like to show two rather convincing sample cases:
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```js
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// How many zeroes is that? Millions? Billions? Trillions?
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const msInOneYear = 31536000000;
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// Is this 4,200 or 42.00 (in cents)?
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const price = 4200;
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// Ok, this is approximately 31.5 billion
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const msInOneYear = 31_536_000_000;
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// Based on the separator, this should be 42.00 (cents)
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const price = 42_00;
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```
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Finally, as far as caveats go, you only need to remember that numbers cannot start or end with a numeric separator and that you can't have two or more numeric separators in a row.
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