js实现base64加密

{

var keyStr = "ABCDEFGHIJKLMNOP" +"QRSTUVWXYZabcdef" +"ghijklmnopqrstuv" +"wxyz0123456789+/" + "=";

var output = "";

var chr1, chr2, chr3 = "";

var enc1, enc2, enc3, enc4 = "";

var i = 0;

do

{

chr1 = input.charCodeAt(i++);

chr2 = input.charCodeAt(i++);

chr3 = input.charCodeAt(i++);

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);

chr1 = chr2 = chr3 = "";

enc1 = enc2 = enc3 = enc4 = "";

} while (i < input.length);

return output;

}