try decode amf according wikipedia's doc

test_amf.js

var data = new Buffer([0x00, 0x03, 0x00, 0x00, 0x00, 0x01, 0x00, 0x1d, 0x42, 0x61, 0x73, 0x65, 0x53, 0x65, 0x72, 0x76, // 16
  0x69, 0x63, 0x65, 0x2e, 0x64, 0x6f, 0x44, 0x69, 0x73, 0x70, 0x61, 0x74, 0x63, 0x68, 0x54, 0x6f, // 32
  0x42, 0x61, 0x74, 0x63, 0x68, 0x00, 0x02, 0x2f, 0x31, 0x00, 0x00, 0x00, 0xdc, 0x0a, 0x00, 0x00, // 47
  0x00, 0x00
]);

var offset = 0;
var version = data.readUInt16BE(offset);
offset += 2;
var headerLen = data.readUInt16BE(offset);
offset += 2;


function readUtf(data) {
  var len = data.readUInt16BE(offset);
  offset += 2;
  var str = data.slice(offset, offset + len);
  offset += len;
  return str.toString();
}

function readLongUtf(data) {

  var len = data.readInt32BE(offset);
  offset += 4;
  var str = data.slice(offset, offset + len);
  offset += len;
  return str.toString();
}

function readAmf0Object(data) {
  var obj = {};
  do {
    var name = readUtf(data);
    console.log( JSON.stringify(name), name.length );
    if(name.length == 0){
      var endObj = data.readUInt8(offset) == 0x09;
      if(endObj) {
        return obj
      }
    }
    var value = readAmf0Data(data);

    obj[name] = value;
  } while (true);
}

function readAmf3Data(data) {

}

function readAmf0Data(data) {
  var type = data.readUInt8(offset);
  offset += 1;
  switch (type) {
    case 0x00:
      var ret = data.readDoubleBE(offset);
      offset += 8;
      return ret;
    case 0x01:
      var ret = data.readUInt8(offset);
      offset += 1;
      return ret == 1;
    case 0x02:
      return readUtf(data);
    case 0x03:
      return readAmf0Object(data);
    case 0x05:
      return null;
    case 0x08:
      return readAmf0Array(data);
    case 0x0a:
      return readAmf0Array(data);
    case 0x0b:
      var timeStamp = data.readDoubleBE(offset);
      offset += 8;
      var timeZone = data.readUInt16BE(offset);
      offset += 2;
      return [timeStamp, timeZone];
    case 0x0c:
      return readLongUtf(data);
    case 0x0f:
      return readLongUtf(data);
    case 0x10:
      var name = readUtf(data);
      var body = readAmf0Data(data);
      return {
        name: name,
        body: body
      };
    case 0x11:
      return readAmf3Data(data);
  }
}

function readAmf0Array(data) {
  console.log(data.length, offset);
  var amf0ArrayLen = data.readInt32BE(offset);
  offset += 4;
  var ret = [];
  for (var i = 0; i < amf0ArrayLen; i++) {
    ret.push(readAmf0Data());
  }
  return ret;
}

for (var i = 0; i < headerLen; i++) {
  var header = readUtf(data);
  var required = data.readInt8(offset);
  offset += 1;
  var headerValueLen = data.readUInt16BE(offset);
  offset += 2;
  var headerValue = data.slice(offset, offset + headerValueLen)
  offset += headerValueLen;
}

var bodyLen = data.readUInt16BE(offset);
offset += 2;
for (var j = 0; j < bodyLen; j++) {
  var reqUrl = readUtf(data);
  var respUrl = readUtf(data);
  console.log(reqUrl, respUrl, offset);
  // this seems truely useless 
  var messageBodyLen = data.readInt32BE(offset);
  offset += 4;
  console.log(messageBodyLen, offset);
  var body = readAmf0Data(data);
  console.log(body);
}

var obj = new Buffer([0x03, 0x00, 0x04, 0x6e, 0x61, 0x6d, 0x65, 0x02, 0x00, 0x04, 0x4d, 0x69, 0x6b, 0x65, 0x00, 0x03, 0x61, 0x67, 0x65, 0x00, 0x40, 0x3e, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x05, 0x61, 0x6c, 0x69, 0x61, 0x73, 0x02, 0x00, 0x04, 0x4d, 0x69, 0x6b, 0x65, 0x00, 0x00, 0x09]);
offset = 0;
console.log(readAmf0Data(obj));