While reading Crockford's page on private members in JavaScript (), a question arose regarding the use of Prototype by developers.
For instance, consider this:
var Foo = new Object();
Foo.bar = function() { alert('Its a bar'); };
var x = Foo;
x.bar();
as opposed to
var Foo = function(){};
Foo.prototype.bar = function(){alert('Its a bar');};
var x = new Foo();
x.bar();
Both implementations achieve the same result, but are they truly identical? Could this impact inheritance at all?
When implementing the prototype pattern, only a single instance of added attributes exist within the prototype.
// Let's create 1000 functions that perform the same functionality
for (var i=0;i<1000;i++) {
Foo = new Object();
Foo.bar = function() { alert('This is a bar'); };
var x = Foo;
x.bar();
}
// Another approach, more commonly used than #1
function Foo() {
this.bar = function () { alert('It\'s a bar'); };
}
for (var i=0;i<1000;i++) {
var x = new Foo;
x.bar();
}
// Create just one function using the prototype pattern
var Foo = function(){};
Foo.prototype.bar = function(){alert('This is a bar');};
for (var i=0;i<1000;i++) {
var x = new Foo();
x.bar();
}
One drawback of the prototype pattern is its inability to access private members.
// Create just one function
var Foo = function(){
var private = 4;
this.baz = function () {
alert(private);
}
};
Foo.prototype.bar = function(){alert(private);};
var x = new foo;
x.bar(); // results in an error as `private` is undefined
x.baz(); // works fine
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