text: var utf8Encode = require('utf8-encode');
  var keyStr = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';
  
  module.exports = encode;
  function encode(input) {
    var output = '';
    var chr1, chr2, chr3, enc1, enc2, enc3, enc4;
    var i = 0;
  
    input = utf8Encode(input);
  
    while (i < input.length) {
  
      chr1 = input.charCodeAt(i++);
      chr2 = input.charCodeAt(i++);
      chr3 = input.charCodeAt(i++);
  
      if (chr1 > 0xFF || chr2 > 0xFF || chr3 > 0xFF) {
        window.alert(chr1 + ' ' + chr2 + ' ' + chr3);
      }
  
      enc1 = chr1 >> 2;
      enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
      enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
      enc4 = chr3 & 63;
  
      if (isNaN(chr2)) {
        enc3 = enc4 = 64;
      } else if (isNaN(chr3)) {
        enc4 = 64;
      }
  
      output = output +
        keyStr.charAt(enc1) + keyStr.charAt(enc2) +
        keyStr.charAt(enc3) + keyStr.charAt(enc4);
  
    }
  
    return output;
  }
  