37 lines
1.3 KiB
Markdown
37 lines
1.3 KiB
Markdown
---
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title: Pretty-print number of bytes
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tags: string,math
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cover: digital-nomad
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firstSeen: 2018-01-01T18:20:09+02:00
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lastUpdated: 2020-10-22T20:24:04+03:00
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---
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Converts a number in bytes to a human-readable string.
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- Use an array dictionary of units to be accessed based on the exponent.
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- Use `Number.prototype.toPrecision()` to truncate the number to a certain number of digits.
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- Return the prettified string by building it up, taking into account the supplied options and whether it is negative or not.
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- Omit the second argument, `precision`, to use a default precision of `3` digits.
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- Omit the third argument, `addSpace`, to add space between the number and unit by default.
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```js
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const prettyBytes = (num, precision = 3, addSpace = true) => {
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const UNITS = ['B', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'];
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if (Math.abs(num) < 1) return num + (addSpace ? ' ' : '') + UNITS[0];
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const exponent = Math.min(
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Math.floor(Math.log10(num < 0 ? -num : num) / 3),
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UNITS.length - 1
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);
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const n = Number(
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((num < 0 ? -num : num) / 1000 ** exponent).toPrecision(precision)
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);
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return (num < 0 ? '-' : '') + n + (addSpace ? ' ' : '') + UNITS[exponent];
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};
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```
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```js
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prettyBytes(1000); // '1 KB'
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prettyBytes(-27145424323.5821, 5); // '-27.145 GB'
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prettyBytes(123456789, 3, false); // '123MB'
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```
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