How to use javascript to store variables to window correctly?

Question

I am trying to use JSNI (gwt's javacript interface) to set/get variable to/from js object:window like this:

private final native <T> T get(String key)/*-{
    return $wnd.key;
}-*/;


private final native void set(String key, Object value)/*-{
    $wnd.key = value;
}-*/;

///// js equivalent should like this

function get(String key){
    return window.key;
}


function set(String key, var value){
    window.key = value;
}

and if I set a variable: var_1 to window:

var var_1={"id":"id_1","name":"name_1"} 
set("key_1",var_1)

then

get("key_1")

I will get var_1 correctly

and then set another variable var_2 to window

var var_2={"id":"id_2","name":"name_2"} 
set("key_2",var_2)

then,try to get key_1 again

get("key_1")

unexpectedly,var_2 will be returned

so,the problem is obvious:the get() function will always return the last set variable no matter what key is.Questions are:

1,Why?
2,How to make it right?

Alex Luya · Accepted Answer · 2014-11-02 10:44:50Z

1

After Changing to

private final native <T> T get(String key)/*-{
    return $wnd[key];
}-*/;


private final native void set(String key, Object value)/*-{
    $wnd[key] = value;
}-*/;

Both set and get work as expected now.

answered Nov 2, 2014 at 10:44

Alex Luya

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1 Comment

Boris Brudnoy Over a year ago

Seems like you demonstrated that in JS the dot notation refinement is always literal, whereas refinement via "[]" operator results in variable resolution. I didn't know this fine detail of the language - thank you.

Manolo Carrasco Moñino · Accepted Answer · 2014-11-03 10:28:59Z

You don't need to deal with JSNI for this, you already have some useful methods in the Element class, so just cast the object Window to an element and that is.

This code should work:

Element window = ScriptInjector.TOP_WINDOW.cast();

window.setPropertyJSO("key_jso", JsArray.createArray()); 
JavaScriptObject jso = window.getPropertyJSO("key_jso")

window.setPropertyBoolean("key_boolean", true); 
boolean b = window.getPropertyBoolean("key_boolean")

// and the same with:
// setPropertyDouble, getPropertyDouble
// setPropertyInt, getPropertyInt
// setPropertyString, getPropertyString
// setPropertyObject, getPropertyObject

If you are using gwtquery, a library I recomend to always import in any gwt project, you can simply do:

import static com.google.gwt.query.client.GQuery.*;

$(window).prop("key", value);
boolean b = $(window).prop("key");
// or
boolean b = $(window).prop("key", Boolean.class);
// And the same with any type (JavaScriptObject, Double, Integer ...)

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