JavaScript Patterns 3.1 Object Literal

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 literalvar car = {goes: "far"};// another way -- using a built-in constructor// warning: this is an antipatternvar 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 objectvar o = new Object();console.log(o.constructor === Object); // true// a number objectvar o = new Object(1);console.log(o.constructor === Number); // trueconsole.log(o.toFixed(2)); // "1.00"// a string objectvar o = new Object("I am a string");console.log(o.constructor === String); // true// normal objects don't have a substring()// method but string objects doconsole.log(typeof o.substring); // "function"// a boolean objectvar o = new Object(true);console.log(o.constructor === Boolean); // true