Understanding Scope on Javascript

Question

I'm understanding "Scope" I found this code, but Im wondering how can I execute the "inner" function, I tried like this:

outer().inner();

but doesn't works

        /* global scope */
        var local = true;
        var global = true;
        function outer() {
            /* local scope */
            var local = true;
            var global = false;

            /* nearest scope = outer */
            local = !global;
            console.log("Local: "+local);
            console.log("Global: "+Global);

            function inner() {
                /* nearest scope = outer */
                local = false;
                global = false;

                /* nearest scope = undefined */
                /* defaults to defining a global */
                public = global;
            }
        }

you can modify the outer function to add a statement to return the inner function "return inner;" and then you could call the inner function as var inner = outer(); inner(); — Praveen
– Praveen, Commented May 29, 2015 at 19:16

M - · Accepted Answer · 2015-05-29 19:41:15Z

2

You could change outer to be an object instead of a function.

/* global scope */
var local = true;
var global = true;
var outer = {
    /* local scope */
    local : true,
    global : false,

    /* nearest scope = outer */
    local : !global,

    showLogs: function(){
        console.log("Local: "+local);
        console.log("Global: "+Global);
    },

    inner: function(){
        local = false;
        global = false;
        public = global;
    }
}

Notice that I'm declaring outer as an object instead of a function with var outer={} That way you can call the functions with outer.inner(); and outer.showLogs();

edited May 29, 2015 at 19:41

answered May 29, 2015 at 19:27

M -

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2 Comments

Isma Haro Over a year ago

Great Thanks! On comment I think I must put commas instead of semicolons :D !

M - Over a year ago

Whoops! You're absolutely right. I just edited it to show commas.

jthomas · Accepted Answer · 2015-05-29 19:19:32Z

1

In order to access inner(), outer() would need to return inner().

Example:

function outer() {
  ...

  return {
     inner: function inner() {
       ...
     }
  };
}

outer().inner();

Another kind of interesting thing that's possible:

function outer() {
  return function inner() {}
}

outer()();

answered May 29, 2015 at 19:19

jthomas

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2 Comments

Isma Haro Over a year ago

Oh Very interesting! The Second one is like an "Anonymous function" inside a function right?

jthomas Over a year ago

Yeah, you don't really need to name that inner function. I just included that for illustration's sake. return function() { } would have worked the same way.

Tony Gustafsson · Accepted Answer · 2015-05-29 19:22:43Z

1

You cannot do that. You can make the inner function a method if you want and call that... like so:

http://output.jsbin.com/wuseqonuxa/2/edit?js,console (You will get the console logging "Im running").

/* global scope */
var local = true;
var global = true;

function outer() {
    /* local scope */
    var local = true;
    var global = false;
    
    /* nearest scope = outer */
    local = !global;
    console.log("Local: "+local);
    console.log("Global: "+global);
    
    this.inner = function () {
        /* nearest scope = outer */
        local = false;
        global = false;
        
        /* nearest scope = undefined */
        /* defaults to defining a global */
        public = global;
        console.log('Im running');
    }
}

var outer = new outer();
outer.inner();

answered May 29, 2015 at 19:22

Tony Gustafsson

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1 Comment

Isma Haro Over a year ago

Is like if inner is a method now? I mean outer is now an Object and inner is a method ?

user95227 · Accepted Answer · 2015-05-29 19:47:49Z

1

While inside outer, you can simply call inner(). It is defined inside outer and can't be called outside of outer as is. However, you can set outer to return 'inner'. @jthomas shows a couple examples of this below.

edited May 29, 2015 at 19:47

answered May 29, 2015 at 19:19

user95227

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Comments

waternova · Accepted Answer · 2015-05-29 19:15:52Z

0

The inner function can only be accessed by code within outer. Code outside of outer cannot access inner.

answered May 29, 2015 at 19:15

waternova

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