a = {name: 'phx', age: 12}
a.merge({gender: 'male'})

In [51]: a = {'name': 'phx', 'age': 12 }

In [52]: a
Out[52]: {'name': 'phx', 'age': 12}

In [53]: a.update({'gender': 'male'})

In [54]: a
Out[54]: {'name': 'phx', 'age': 12, 'gender': 'male'}

var a = { a: 1 };
var b = Object.assign(a, { b: 2 });
// {a: 1, b: 2}