如何用nodejs写入mysql 的blob格式的数据？

So, if the array length equals 4, then the size of blob data in mysql DB must be 4 bytes. And it works fine with numbers less than 128.

var res = "";    
for(var i = 0; i < arr.length; i++) {
    res += String.fromCharCode(arr[i]);
}

But numbers from 128 to 256 takes 2 bytes.

I tried to use nodejs buffer

var Buffer = require('buffer').Buffer,
    buf = new Buffer(arr.length);
for(var i = 0; i < arr.length; i++) {
    buf[i] = arr[i];
}
buf.toString('binary');

but the same result. I have no idea how to make it work.

to store data in mysql database I use node-mysql

var Client = require('mysql').Client,
    client = new Client();
client.user = DB_USER;
client.password = DB_PASS;
client.host = DB_HOST;
client.connect(function(error, results) {
    if(error) {
        client.end();
        return;
    }
    client.query('USE ' + DB_SCHEME, function(error, results) {
        if(error) {
            client.end();
            return;
        }

        var sql = "INSERT INTO b SET `data` = ?";
        var values = [buf];

        client.query(sql, values,
            function(error, results) {
                if(error) {
                    return;
                }
                return;
            }
        );
    });
});