JavaScript Patterns 3.1 Object Literal

Basic concept

Values can be

properties: primitives or other objects

methods: functions

User-defined native objects are mutable at any time.  

Object literal notation is ideal for this type of on-demand object creation.  

Even the simplest {} object already has properties and methods inherited from Object.prototype.

var dog = {
    name: "Benji",
    getName: function () {
        return this.name;
    }
}; 

1. The Object Literal Syntax

   • Wrap the object in curly braces ({ and }).

   • Comma-delimit the properties and methods inside the object. A trailing comma after the last name-value pair is allowed but produces errors in IE, so don't use it.

   • Separate property names and property values with a colon.

   • When you assign the object to a variable, don't forget the semicolon after the closing }.

2. Objects from a Constructor

   // one way -- using a literal
   
   var car = {goes: "far"};
   
   // another way -- using a built-in constructor
   
   // warning: this is an antipattern
   
   var car = new Object();
   
   car.goes = "far";

3. Object Constructor Catch

   Don't use new Object(); use the simpler and reliable object literal instead.

   // Warning: antipatterns ahead
   
   // an empty object
   
   var o = new Object();
   
   console.log(o.constructor === Object); // true
   
   // a number object
   
   var o = new Object(1);
   
   console.log(o.constructor === Number); // true
   
   console.log(o.toFixed(2)); // "1.00"
   
   // a string object
   
   var o = new Object("I am a string");
   
   console.log(o.constructor === String); // true
   
   // normal objects don't have a substring()
   
   // method but string objects do
   
   console.log(typeof o.substring); // "function"
   
   // a boolean object
   
   var o = new Object(true);
   
   console.log(o.constructor === Boolean); // true