This generates a heapdump.

heapdump.js

var profiler = require('v8-profiler');

var MyClass = function(x) {
    this.x = x;
};

MyClass.prototype.getX = function() {
    return x;
};

var a = [1,2,3];
var b = {"a":1};
var c = 6;
var deadbeefisgood = "DEADBEEFMIGHTBEGOOD";

var x = new MyClass(78797);
var xx = x.getX();

var snapshot = profiler.takeSnapshot(["hello"], "full");
console.log(snapshot.stringify());