Prototype vs. Instance

Instance.js

function Person(name) {
  this.name = name;

  this.greet = function() {
    console.log('Hello ' + this.name);
  }

  this.setName = function(name) {
    this.name = name;
  }
}

var cache = [];

for (var i = 0; i < 1e6; i++) {
  cache.push(new Person('Merrick'));
}

console.log(JSON.stringify(process.memoryUsage()));

Output.txt

Prototype creation was cheaper by 145.2164764404297 MB

Prototype.js

function Person(name) {
  this.name = name;
}

Person.prototype.greet = function() {
  console.log('Hello ' + this.name);
}

Person.prototype.setName = function(name) {
  this.name = name;
}

var cache = [];

for (var i = 0; i < 1e6; i++) {
  cache.push(new Person('Merrick'));
}

console.log(JSON.stringify(process.memoryUsage()));

run.js

var exec = require('child_process').exec;
var mb = 1048576;

exec('node Instance.js',
  function (error, stdout, stderr) {
    var instance = JSON.parse(stdout);

    exec('node Prototype.js',
      function (error, stdout, stderr) {
        var proto = JSON.parse(stdout);
        
        if (instance.heapUsed < proto.heapUsed) {
          console.log('Instance creation was cheaper by '+ ((proto.heapUsed - instance.heapUsed) / mb)+ ' MB');
        } else {
          console.log('Prototype creation was cheaper by '+ ((instance.heapUsed - proto.heapUsed)/ mb)+ ' MB');
        }

      });
  }
);