Module base64

URL-safe base64 string codec.

Provides a symmetric encoder/decoder pair (encodeBase64, decodeBase64) for safely carrying arbitrary Unicode text in URLs and application/x-www-form-urlencoded payloads. Wraps the standard btoa / atob primitives, addressing two limitations that make them unsuitable on their own for 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). The codec adopts the URL-safe variant of RFC 4648 § 5, mapping + / / to - / _ on encode (and back on decode) and stripping the trailing = padding. Decoding accepts both padded and unpadded input.

Usage

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

encodeBase64("hello");    // "aGVsbG8" — trailing `=` padding stripped
encodeBase64(">>>");      // "Pj4-"    — standard `+` remapped to `-`
encodeBase64("???");      // "Pz8_"    — standard `/` remapped to `_`
encodeBase64("日");        // "5pel"    — multi-byte UTF-8

decodeBase64("aGVsbG8");  // "hello"   — unpadded input accepted
decodeBase64("aGVsbG8="); // "hello"   — padded input accepted
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