console.clear();

var person = mobx.observable({
	firstName: 'Matt',
	lastName: 'Ruby',
	age: 25
});

mobx.autorun(function () {
	console.log(person.firstName + ' ' + person.age);
});

_.times(10, function () {
	person.age = _.random(40);
});

@@ -178,16 +178,52 @@
 );%0A%7D);%0A%0A
+// this will print Matt NN 10 times%0A
 _.times(
@@ -268,12 +268,102 @@
 om(40);%0A%7D);%0A
+%0A// this will print nothing%0A_.times(10, function () %7B%0A%09person.lastName = _.random(40);%0A%7D);

Simplified the example