// define struct
var struct = {
  foo: 0,
  bar: 127,
  baz: {
    qux: 65535
  }
};

// write arraybuffer from javascript object
var ab = new ArrayBuffer(4);
var dv = new DataView(ab);
dv.setUint8(0, struct.foo);
dv.setInt8(1, struct.bar);
dv.setUint16(2, struct.baz.qux, true);

console.log(dv.buffer);
// => ArrayBuffer {byteLength: 4, slice: function}

// read data from arraybuffer
var dv2 = new DataView(dv.buffer);
var data = {
  foo: dv2.getUint8(0),
  bar: dv2.getInt8(1),
  baz: {
    qux: dv2.getUint16(2, true)
  }
};

console.log(data);
// => Obejct {foo: 0, bar: 127, baz: {qux: 65535}}

/**
 * create struct
 *
 * @param {object} data object
 * @param {number} default value[optional, default 0]
 * @param {boolean} endian[optional, default true]
 */

var struct = new Struct({
  foo: 'uint8',
  bar: ['int8', 127],
  baz: {
    qux: ['uint16', 65535]
  }
}, 0, true);

  
/**
 * write arraybuffer from javascript object
 *
 * @param {object} for update[optional]
 */

var ab = struct.write();
// => ArrayBuffer {byteLength: 4, slice: function}


/**
 * read data object from arraybuffer
 *
 * @param {object} arraybuffer
 * @param {number} offset[optinal, default 0]
 */

struct.read(ab);
// => Obejct {foo: 0, bar: 127, baz: {qux: 65535}}


/**
 * update data of arrayBuffer with write and read methods
 */

var ab2 = struct.write({foo: 255, baz: {qux: 0}});
// => ArrayBuffer {byteLength: 4, slice: function}

struct.read(ab2);
// => Obejct {foo: 255, bar: 127, baz: {qux: 0}}

/**
 * read data with custom offset
 */

var struct = new Struct({
  sig: 'uint8',
  mimeType: 'uint8',
  id: 'uint16',
  byteLength: 'uint32'
});

...

function parseBinary(count, chunk, callback) {
  var offset = 0;
  for (var index = 0; index < count; index++) {
    var meta = struct.read(chunk, offset)
      , buffer = chunk.slice(
        offset += struct.byteLength,
        offset += meta.byteLength
      );

    callback(meta, new Uint8Array(buffer));
  }
}

/**
 * create struct with multi-byte value
 */

var struct = new Struct({
  foo: ['uint16', [0xffff, 4095]],
  bar: ['uint8', 'firejune', 8]
});

var ab = struct.write();
// => ArrayBuffer {byteLength: 12, slice: function}

var obj = struct.read(ab);
// => Object {bar: [65535, 4095], qux: "firejune"}