var prettyFormat = require('pretty-format');

var obj = { property: {} };
obj.circularReference = obj;
obj[Symbol('foo')] = 'foo';
obj.map = new Map();
obj.map.set('prop', 'value');
obj.array = [1, NaN, Infinity];

console.log(prettyFormat(obj));

Object {
  "property": Object {},
  "circularReference": [Circular],
  "map": Map {
    "prop" => "value"
  },
  "array": Array [
    1,
    NaN,
    Infinity
  ],
  Symbol(foo): "foo"
}

var fooPlugin = {
  test: function(val) {
    return val && val.hasOwnProperty('foo');
  },
  print: function(val, print, indent) {
    return 'Foo: ' + print(val.foo);
  }
};

var obj = { foo: { bar: {} } };

prettyFormat(obj, {
  plugins: [fooPlugin]
});
// Foo: Object {
//   "bar": Object {}
// }

var prettyFormat = require('pretty-format');
var reactTestPlugin = require('pretty-format/plugins/ReactTestComponent');
var reactElementPlugin = require('pretty-format/plugins/ReactElement');

var React = require('react');
var renderer = require('react/lib/ReactTestRenderer');

var jsx = React.createElement('h1', null, 'Hello World');

prettyFormat(renderer.create(jsx).toJSON(), {
  plugins: [reactTestPlugin, reactElementPlugin]
});
// <h1>
//   Hello World
// </h1>