How to Set this in Javascript

I have the following setup:

var Dash = {
    nextIndex: 0,
    dashboards: <some value>,

    display: function()
    {
        var dashboard = Dash.dashboards[Dash.nextIndex];
        doc开发者_如何学编程ument.getElementById("iframe3").src = dashboard.url;
        Dash.nextIndex = (Dash.nextIndex + 1) % Dash.dashboards.length;
        setTimeout(Dash.display, dashboard.time * 1000);
    }
};

With this setup, is it possible to set programmatically, the value of "some value" prior to this declaration?

In addition, is it possible to have be a javascript function call that retunrs a value to dashboards?

Thanks.

Not prior (short of dummy values like null) but you can do so afterwards using Dash.dashboards= some-value;

No.

You would have to define Dash in order to define Dash.dashboards, and as soon as your listed code runs it is all overwritten.

So, no.

Javascript has lexical scoping and not block scoping . What that means is that all variable declaration in javascript are shifted to the top of the function .

So the code that you wrote is internally changed to something like :

    var Dash = undefined ;
   // other lines of codes 
    Dash = {
        nextIndex: 0,
        dashboards: some_value,

        display: function()
        {
            var dashboard = Dash.dashboards[Dash.nextIndex];
            document.getElementById("iframe3").src = dashboard.url;
            Dash.nextIndex = (Dash.nextIndex + 1) % Dash.dashboards.length;
            setTimeout(Dash.display, dashboard.time * 1000);
        }
    };

So you basically want to access the value of Dash.dashboard before Dash is assigned, which would fail as Dash is undefined . and undefined.dashboard would give you an error . However you could definitely call a function in the assignment operation that populates some_value

var Dash = {
        dashboards: function_call()
}

Btw , why exactly would you want to use Dash.dashboard before the assignment operation ? If you could let us know that , there might be a better way of doing it .

You can not . Dash would be undefined until it is assigned . so Dash.dashboard would not be accesible .

How about this?

dashboards: null,

To set some value to dashboards

Dash.dashboards = "something"

As dashboards is going to hold an array I would use an empty array: dashbords: []