How can I add an object property to the global object in rhino javascript

Question

I have some properties in an object that I would like to add to the global namespace. In javascript on the browser I could just add it to the window object like so:

var myObject = {
  foo : function() {
    alert("hi");
  }
  // and many more properties
};

for (property in myObject) {
  window[property] = myObject[property];
}

// now I can just call foo()
foo();

But since rhino doesn't have the global window object I can't do that. Is there an equivalent object or some other way to accomplish this?

Giacobo

I figured out how to do it without having to write extra javascript: https://mcmap.net/q/907574/-how-do-i-call-a-method-of-a-java-instance-from-javascript – Lohrman

Answer 1

You could use this, which refers to the global object if the current function is not called as a method of an object.

Hotbox

var window = this; at the very beginning of the script helped me out. See the env.js script by John Resig ejohn.org/blog/bringing-the-browser-to-the-server – Fugue

@Miles, Hmm, don't you think that pnewhook's solution is better? – Hornbeck

Answer 2

I found a rather brilliant solution at NCZOnline:

function getGlobal(){
  return (function(){
    return this;
    }).call(null);
}

The key to this function is that the this object always points to the global object anytime you are using call() or apply() and pass in null as the first argument. Since a null scope is not valid, the interpreter inserts the global object. The function uses an inner function to assure that the scope is always correct.

Call using:

var glob = getGlobal();

glob will then return [object global] in Rhino.

Taxis

Brilliant! Remember that this will not work in ES5 strict mode, so your script may fail once Rhino introduces ES5-conformance. – Nimrod

cool thanks. function getGlobal(){return (function(){return this})()} is simpler and equivalent (confirmed by the author) – Woadwaxen

@user123444555621, Why wouldn't this work in ES5 strict mode? – Hornbeck

It will return null instead: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… – Hotbox

Jsfiddle showing that this does not work in ES5 strict mode even if getGlobal itself doesn't have "use strict" (but is within another function that is marked as "use strict" – Rheinlander

Answer 3

Here's how I've done it in the past:

// Rhino setup
Context jsContext = Context.enter();
Scriptable globalScope = jsContext.initStandardObjects();

// Define global variable
Object globalVarValue = "my value";
globalScope.put("globalVarName", globalScope, globalVarValue);

Tuneberg

Why not simply use this? – Hornbeck

Answer 4

You could just define your own window object as a top-level variable:

var window = {};

You can then assign values to it as you please. ("window" probably isn't the best variable name in this situation, though.)

See also: Can I create a 'window' object for javascript running in the Java6 Rhino Script Engine

Reprove

Answer 5

I've not used rhino but couldn't you just use var?

i.e.

var foo = myObject.foo;
foo();

Edit: Damn knew there'd be a catch! Miles' suggestion would be the go in that case.

Superfluity

Hah! Too simple for me :) Thanks! – Giacobo

Ah, wait...here's my real problem. I want to do this programmaticaly. I don't actually know the names of the object properties before hand. – Giacobo

This answer is unfortunately just clutter, as such could it be deleted? No hard feelings! – Friulian