CODEWITHSUNDEEP
javascriptprototype
jsnewman
jsnewman

Reputation: 339

a prototype question in javascript

<script type="text/javascript">

var Person =
{

    Create: function(name, age) {  
        this.name = name;
        this.age = age;
    },
    showMe: function() {
        return " Person   Name: " + this.name + "  Age: " + this.age + " ";
    }
}; 

function New(aClass, aParams) {
    function new_() { 
        aClass.Create.apply(this, aParams);  
    };
    new_.prototype = aClass;   
    var obj = new new_();  
    return obj;
}
</script>

I don't quite understand the code above. Could someone tell me the meanings of Person, Create, showMe, New and new_? Thanks a lot.

Upvotes: -1

Views: 169

Answers (2)

Stoive
Stoive

Reputation: 11332

Person is an object with two functions - Create and showMe. In JavaScript, there are no classes, only objects, and this is how you write up an object - using 'Object Literal Notation' (the curly braces and functions/properties separated by commas).

New is a clever re-implementation of the new keyword. Instead of classes, javascript has prototypes, and instead of creating an instance of a class you create a copy of the prototype. In this case, if you passed Person to New(), it would used as the prototype in new_.prototype = aClass, and the rest of this function will return an object with the Person prototype, which means any changes to Person later on will be inherited into obj as well (unless obj has overridden them).

Upvotes: 2

jon_darkstar
jon_darkstar

Reputation: 16788

`Person` -- a variable w/ 'parts' (used loosely) `Person.Create` and `Person.showMe'
     `Person.Create` -- function of `Person` that sets `Person.name` and `Person.age` to its arguments
     `Person.showMe` -- returns a string explaining values of `Person.name` and `Person.age`

`New` -- a function intended to instantiate new Person's thru prototypal (this is NOT class based) inheritenced
  `New._new` -- `New` uses this to get it done

Basically thru prototype inheritence, even though Person is only 'made' once, other 'versions' of it can be constructed in kind. It can be used like this (try it here: http://jsfiddle.net/PBhCs/)

var Person =    {            
    Create: function(name, age) 
    {              
        this.name = name;            
        this.age = age
    },        

    showMe: function() 
    {            
        return " Person   Name: " + this.name + "  Age: " + this.age + " ";        
    }    
};         


function New(aClass, aParams) 
{        
    function new_() 
    {             
        aClass.Create.apply(this, aParams);          
    };
    new_.prototype = aClass;
    var obj = new new_();          
    return obj;    
}   

var a = New(Person, ['moo', 5]);
var b = New(Person, ['arf', 10]);
alert(a.showMe() + b.showMe());

Upvotes: 0

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