JSPatterns.com

A simple way to create objects in JavaScript is using object literal notation. An other way, a bit more involved is to use a constructor function.

var adam = new Person("Adam");
adam.say(); // "I am Adam"

The invocation of the constructor looks a bit like a class in other languages, but the constructor is still just a function. (JavaScript doesn’t have classes). So the constructor is the blueprint, the recipe for the object.

And here's how the constructor Person is defined, it adds all members to the this object.

var Person = function(name) {

  this.name = name;
  this.say = function() {
    return "I am " + this.name;
  };

};

When you define a constructor, something like the following happens behind the scenes. It's as if you defined an object using the literal notation and then returned it.

var Person = function(name) {
  // var this = {};
  this.name = name;
  this.say = function() {
    return “I am ” + this.name;
  };
  // return this;
};

Tags: constructors, Object creation patterns

This entry was posted on Monday, September 14th, 2009 and is filed under Object creation patterns. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.