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
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