function base64Decode(text){
        
    //ignore white space
    text = text.replace(/\s/g,"");
        
    //first check for any unexpected input
    if(!(/^[a-z0-9\+\/\s]+\={0,2}$/i.test(text)) || text.length % 4 > 0){
        throw new Error("Not a base64-encoded string.");
    }    

    //local variables
    var digits = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
        cur, prev, digitNum,
        i=0,
        result = [];

    //remove any equals signs
    text = text.replace(/=/g, "");
        
    //loop over each character
    while(i < text.length){
        
        cur = digits.indexOf(text.charAt(i));
        digitNum = i % 4;
        
        switch(digitNum){
                
            //case 0: first digit - do nothing, not enough info to work with
            
            case 1: //second digit
                result.push(String.fromCharCode(prev << 2 | cur >> 4));
                break;
                
            case 2: //third digit
                result.push(String.fromCharCode((prev & 0x0f) << 4 | cur >> 2));
                break;
                
            case 3: //fourth digit
                result.push(String.fromCharCode((prev & 3) << 6 | cur));
                break;
        }
        
        prev = cur;
        i++;
    }
    
    //return a string
    return result.join("");

}
Base64-decodes a string of text.
@param {String} text The text to decode.
@return {String} The base64-decoded string.