js Base64加密

// base64加密开始
var keyStr = “ABCDEFGHIJKLMNOP” + “QRSTUVWXYZabcdef” + “ghijklmnopqrstuv”
+ “wxyz0123456789+/” + “=”;

function encode64(input) {

    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;
}