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POObject Oriented questions in Javascript
 

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    <p>I've been using javascript for a while, but have never learned the language past the basics. I am reading John Resig's "Pro Javascript Techniques" - I'm coming up with some questions, but I'm not finding the answers to them in the book or on google, etc.</p> <p>John gives this example in his book:<br /> <strong>Function #1</strong></p> <pre><code>function User( name, age ){ this.name = name; this.age = age; } // Add a new function to the object prototype User.prototype.getName = function(){ return this.name; }; User.prototype.getAge = function(){ return this.age; }; var user = new User( "Bob", 44 ); console.log("User: " + user.getName() + ", Age: " + user.getAge()); </code></pre> <p>I'm still learning about the <em>prototype</em> property, so I tried writing something similar:<br /> <strong>Function #2</strong></p> <pre><code>function User (name, age ) { this.name = name; this.age = age; this.getName = function() { return this.name; }; this.getAge = function() { return this.age; }; } var user = new User( "Bob", 44 ); console.log("User: " + user.getName() + ", Age: " + user.getAge()); </code></pre> <p>It doesn't use the <em>prototype</em> property to create the getName and getAge functions, but the output is the same as John's example.</p> <p>I took it one step further, and created this:<br /> <strong>Function #3</strong></p> <pre><code>var User = { name: "", age: 0, setName: function(name) { this.name = name; }, setAge: function(age) { this.age = age; }, getName: function() { return this.name; }, getAge: function() { return this.age; } }; User.setName("Bob"); User.setAge(44); console.log("User: " + User.getName() + ", Age: " + User.getAge()); </code></pre> <p>Again - it looks different than John's example (and I had to add setter methods), but the output is the same.</p> <p><strong>Question #1</strong> - what is the difference between the 3 functions? What is the advantage of the prototype property, and is Function #2 doing anything incorrectly, because it seems more straight forward to code #2 instead of #1 (although I'm sure #1 is doing it better seeing as John created it).</p> <p><strong>Question #2</strong> - How could I modify function #3 to not use the setName and setAge methods, but still keep the {...} shorthand? Can the {...} shorthand have constructors?</p> <p>Thanks in advance for helping me learn!</p> <p><strong>EDIT</strong> I think my 2nd question was a little confusing. I meant how could I use the {...} shorthand to create a User object, but then after I create the object, say something like:</p> <pre><code>var user = new User("Bob", 44); </code></pre> <p>Just like in Function #1 - or is that not possible?</p> <p><strong>EDIT #2</strong> Wow! Thanks everyone for the awesome answers. That really makes it a lot more clear to me. So if I understand correctly, the difference between #1 and #2 aren't too much. If I only ever create one "User" object - they probably aren't different at all. But if my program creates many User objects, #1 would most likely be more efficient and use less memory since all objects will share the same functions.</p> <p>I really appreciate all of the great answers - Thanks!</p>
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