jsBase64

original:https://www.npmjs.com/package/js-base64
Encode
let latin = 'dankogai';
let utf8  = '小飼弾'
let u8s   =  new Uint8Array([100,97,110,107,111,103,97,105]);
Base64.encode(latin);             // ZGFua29nYWk=
Base64.encode(latin, true));      // ZGFua29nYWk skips padding
Base64.encodeURI(latin));         // ZGFua29nYWk
Base64.btoa(latin);               // ZGFua29nYWk=
Base64.btoa(utf8);                // raises exception
Base64.fromUint8Array(u8s);       // ZGFua29nYWk=
Base64.fromUint8Array(u8s, true); // ZGFua29nYW which is URI safe
Base64.encode(utf8);              // 5bCP6aO85by+
Base64.encode(utf8, true)         // 5bCP6aO85by-
Base64.encodeURI(utf8);           // 5bCP6aO85by-

Decode

Base64.decode(      'ZGFua29nYWk=');// dankogai
Base64.decode(      'ZGFua29nYWk'); // dankogai
Base64.atob(        'ZGFua29nYWk=');// dankogai
Base64.atob(        '5bCP6aO85by+');// '小飼弾' which is nonsense
Base64.toUint8Array('ZGFua29nYWk=');// u8s above
Base64.decode(      '5bCP6aO85by+');// 小飼弾
// note .decodeURI() is unnecessary since it accepts both flavors
Base64.decode(      '5bCP6aO85by-');// 小飼弾