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

The pretty-bytes library formats byte counts using a multi-step process implemented in the main prettyBytes function [index.js:L124-L179]:

Core Logic:

1. Input Validation: The function first checks that the input is a finite number or bigint, throwing a TypeError if not [index.js:L125-L127].

2. Unit Selection: It selects the appropriate unit system based on options:

   • bits option: uses BIT_UNITS or BIBIT_UNITS
   • binary option: uses BIBYTE_UNITS or BYTE_UNITS (default is decimal SI prefix) [index.js:L140-L142]

3. Exponent Calculation: For numbers ≥ 1, it calculates which unit tier to use by computing the exponent. For binary format, it uses log(number) / Math.log(1024), while decimal format uses log10(number) / 3. The result is clamped to the maximum available unit [index.js:L159].

4. Number Scaling: The number is divided by either 1024^exponent (binary) or 1000^exponent (decimal) to scale it appropriately [index.js:L160].

5. Localization & Formatting: If no locale is specified, it applies precision formatting; otherwise, it uses toLocaleString() with locale-specific options [index.js:L162-L168].

6. Output Assembly: The result combines a prefix (for signed numbers), the formatted number, a separator (space or non-breaking space), and the unit [index.js:L170].

Example: prettyBytes(1337) returns '1.34 kB' because 1337 bytes falls into the kilobyte range and is formatted with appropriate precision.

The function also handles edge cases like negative numbers, zero, numbers less than 1, and extremely large values exceeding exabytes [index.js:L147-L158].

FOLLOW_UPS:

• What options can customize the formatting behavior?
• How does the function handle bigint inputs differently?
• What's the difference between binary and decimal formatting?