utf-8-base64.js

/**
 *　遗留的问题: 这是utf-8 ??
 *  关于encodeURIComponent 与 encodeURI 的最佳实践 
 *  http://stackoverflow.com/questions/75980/best-practice-escape-or-encodeuri-encodeuricomponent
 *
Unicode Strings

In most browsers, calling window.btoa on a Unicode string will cause a Character Out Of Range exception.

To avoid this, consider this pattern, noted by Johan Sundström
(http://ecmanaut.blogspot.com/2006/07/encoding-decoding-utf8-in-javascript.html):

*/
function utf8_to_b64( str ) {
    return window.btoa(unescape(encodeURIComponent( str )));
}

function b64_to_utf8( str ) {
    return decodeURIComponent(escape(window.atob( str )));
}

// Usage:
utf8_to_b64('✓ à la mode'); // "4pyTIMOgIGxhIG1vZGU="
b64_to_utf8('4pyTIMOgIGxhIG1vZGU='); // "✓ à la mode"