Obtener el tamaño de un objeto a partir de sus llaves

app.js

var var_object = {
  'one': 'The first key',
  'two': 'The second key',
  'three': 'The third key'
};

var size_object = Object.keys(var_object).length;

console.log('The size is: ' + size_object); // The size is: 3 ;