Js base64 加密解密

<script type="text/javascript">


var base64encodechars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
var base64decodechars = new Array(
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1);


 


function base64encode(str) {
 var out, i, len;
 var c1, c2, c3;
 len = str.length;
 i = 0;
 out = "";
 while (i < len) {
  c1 = str.charCodeAt(i++) & 0xff;
  if (i == len) {
   out += base64encodechars.charAt(c1 >> 2);
   out += base64encodechars.charAt((c1 & 0x3) << 4);
   out += "==";
   break;
  }
  c2 = str.charCodeAt(i++);
  if (i == len) {
   out += base64encodechars.charAt(c1 >> 2);
   out += base64encodechars.charAt(((c1 & 0x3) << 4) | ((c2 & 0xf0) >> 4));
   out += base64encodechars.charAt((c2 & 0xf) << 2);
   out += "=";
   break;
  }
  c3 = str.charCodeAt(i++);
  out += base64encodechars.charAt(c1 >> 2);
  out += base64encodechars.charAt(((c1 & 0x3) << 4) | ((c2 & 0xf0) >> 4));
  out += base64encodechars.charAt(((c2 & 0xf) << 2) | ((c3 & 0xc0) >> 6));
  out += base64encodechars.charAt(c3 & 0x3f);
 }
 return out;
}


function base64decode(str) {
 var c1, c2, c3, c4;
 var i, len, out;


 len = str.length;


 i = 0;
 out = "";
 while (i < len) {


  do {
   c1 = base64decodechars[str.charCodeAt(i++) & 0xff];
  } while (i < len && c1 == -1);
  if (c1 == -1)
   break;




  do {
   c2 = base64decodechars[str.charCodeAt(i++) & 0xff];
  } while (i < len && c2 == -1);
  if (c2 == -1)
   break;


  out += String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4));




  do {
   c3 = str.charCodeAt(i++) & 0xff;
   if (c3 == 61)
    return out;
   c3 = base64decodechars[c3];
  } while (i < len && c3 == -1);
  if (c3 == -1)
   break;


  out += String.fromCharCode(((c2 & 0xf) << 4) | ((c3 & 0x3c) >> 2));




  do {
   c4 = str.charCodeAt(i++) & 0xff;
   if (c4 == 61)
    return out;
   c4 = base64decodechars[c4];
  } while (i < len && c4 == -1);
  if (c4 == -1)
   break;
  out += String.fromCharCode(((c3 & 0x03) << 6) | c4);
 }
 return out;
}


</script>