How does pretty-bytes format byte counts into a human-readable string?

The prettyBytes function converts byte counts into human-readable strings by using a multi-step process:

Unit Selection

First, the function selects the appropriate unit array based on the options provided [index.js:L138-L140]:

• Bytes (default): Uses BYTE_UNITS (B, kB, MB, GB, TB, PB, EB, ZB, YB) with base-10 (1000)
• Bits: Uses BIT_UNITS (b, kbit, Mbit, etc.) with base-10
• Binary Bytes: Uses BIBYTE_UNITS (B, KiB, MiB, GiB, etc.) with base-2 (1024)
• Binary Bits: Uses BIBIT_UNITS (b, kibit, Mibit, etc.) with base-2

Exponent Calculation

The function determines which unit to use by calculating an exponent [index.js:L161-L162]:

• For decimal: Math.floor(log10(number) / 3)
• For binary: Math.floor(log(number) / Math.log(1024))

This exponent corresponds to the index in the unit array.

Number Formatting

The number is then divided by the appropriate power (1000 or 1024) and formatted with precision [index.js:L163-L168]. If no locale is specified, precision is calculated to show at least 3 significant figures.

Result Assembly

Finally, the result is assembled by combining the prefix (for signed numbers), the formatted number, an optional separator (space or non-breaking space), and the appropriate unit [index.js:L170-L171].

For example, 1337 becomes 1.34 kB because 1337 ÷ 1000 = 1.34, and the unit at exponent 1 is kB.

FOLLOW_UPS:

• What unit arrays are available for different formats?
• How does the signed option work in prettyBytes?
• How is locale-based number formatting handled?