Module base64

RFC 4648 base64 encoders and decoders * Provides a symmetric encoder/decoder pair (encodeBase64, decodeBase64) for carrying arbitrary Unicode text as base64, either in the standard alphabet of RFC 4648 § 4 or in the URL-safe variant of RFC 4648 § 5. Wraps the standard btoa / atob primitives, addressing two limitations that make them unsuitable on their own for Unicode and URL-bound text:

• btoa / atob accept only binary (Latin-1) strings and throw on any code point above 0xFF. The codec routes input through TextEncoder / TextDecoder to convert between JavaScript strings and UTF-8 byte sequences before delegating to the standard primitives, making multi-byte characters such as "日" transparently encodable.

• The standard base64 alphabet uses +, /, and =, all of which carry special meaning in URLs and application/x-www-form-urlencoded payloads (+ is interpreted as space, / as a path separator, = as the key/value separator). encodeBase64 accordingly takes a url flag selecting the URL-safe variant of RFC 4648 § 5, which maps + / / to - / _ and strips the trailing = padding. decodeBase64 needs no such flag: it accepts either alphabet, padded or unpadded.

Usage

import { encodeBase64, decodeBase64 } from "@metreeca/core/base64";

encodeBase64("hello");       // "aGVsbG8=" — standard alphabet, `=` padding retained
encodeBase64(">>>");         // "Pj4+"     — standard `+` retained
encodeBase64("???");         // "Pz8/"     — standard `/` retained
encodeBase64("日");           // "5pel"     — multi-byte UTF-8

encodeBase64("hello", true); // "aGVsbG8"  — URL-safe: trailing `=` padding stripped
encodeBase64(">>>", true);   // "Pj4-"     — URL-safe: `+` remapped to `-`
encodeBase64("???", true);   // "Pz8_"     — URL-safe: `/` remapped to `_`

decodeBase64("aGVsbG8");     // "hello"    — unpadded input accepted
decodeBase64("aGVsbG8=");    // "hello"    — padded input accepted
decodeBase64("Pj4+");        // ">>>"      — standard alphabet accepted
decodeBase64("Pj4-");        // ">>>"      — URL-safe alphabet accepted
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