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;
}
};
- 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 }.
- 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";
- 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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