javascript accessing a member function from outer scope variable

Question

I have been trying out some js code in jsfiddle and it seems I cant get all these combinations of codes below to work..

//combination #1    
function get_set() {
    this.get = function () {
        document.write("get");
    };
    this.set = function () {
        document.write("set");
    };
};

var x = get_set; // storing function reference in x
x.get(); //invoking doesnt work.

//combination#2
var get_set = function() {
    this.get = function () {
        document.write("get");
    };
    this.set = function () {
        document.write("set");
    };
};

get_set.get(); //doesnt work as well..

Is there something that I miss? Thanks in advance for constructive suggestion/pointing out any errors. Would appreciate any help.

Florian · Accepted Answer · 2011-06-28 04:59:26Z

4

You either have to create a new instance of get_set

var x = new get_set();

or inside get_set you have to use return this; for this example to work.

answered Jun 28, 2011 at 4:59

Florian

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2 Comments

RobG Over a year ago

The return this part is not good advice. If called without new, this will be the global/window object so this.get assigns a function to a global variable called get and similarly for this.set.

KooiInc Over a year ago

Additionaly, returning this from a function call doesn't create unique instances. So if this is returned, in var a=get_set(), b=get_set(); b.set = 'I have changed' a.set now also has the value 'I have changed'

KooiInc · Accepted Answer · 2011-06-28 06:15:06Z

3

Your get_set function is a constructor function. It's intended to create ('construct') instances of itself. In order to make that work you need the keyword new. So

var getset = new get_set;

creates an instance of get_set. Now the methods getset.set and getset.get are available.

In this case maybe you could create a unique instance using an Object literal:

var get_set = {
    get: function () {
        document.write("get");
    },
    set: function () {
        document.write("set");
    }
};

Now you don't need the new keyword and the methods are available right away (get_set.get, get_set.set)

edited Jun 28, 2011 at 6:15

answered Jun 28, 2011 at 5:15

KooiInc

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2 Comments

RobG Over a year ago

Perhaps, but now the OP can't make instances of get_set, but maybe that isn't needed anyway.

KooiInc Over a year ago

Hi RobG, it was a suggestion. I changed the wording of my answer a little bit.

Troy SK · Accepted Answer · 2011-06-28 04:58:44Z

0

Use x=new get_set; That will work.

answered Jun 28, 2011 at 4:58

Troy SK

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