How to send values from javascript to julia using WebIO?

Question

I'm struggling to understand how to use WebIO. From the documentation, this would be an example to send values to javascript:

using WebIO
s = Scope()
obs = Observable(s, "logme", "")
onjs(
    s, "logme",
    js"""
    function(newValue) {
        console.log(newValue);
    }
    """
)

Now, in order to test this, I run it in the REPL followed by

using Mux
WebIO.webio_serve(
    page("/", req -> s)
)

then point my browser (Brave) to localhost:8000 and open the console (via developer tools). At this point, I expect that running obs[] = "hi there" in the REPL would make that message show up in the console. But nothing happens. Why is my understanding of the expected behavior wrong? What should I do to make the javascript console log a message that I write to an observable on the julia side?

Oskar · Accepted Answer · 2022-03-30 09:44:17Z

1

I guess there is an error in the documentation. The problem is that there are no listeners on the observable. I.e., julia> obs returns Observable{String} with 0 listeners. You can add a listener by WebIO.ensure_sync(s, "logme"), or you can write it like this:

using Mux, WebIO, JSExpr
s = Scope()
obs = Observable(s, "logme",  "")
onjs(obs,
     js"""
     function(newValue) {
        console.log(newValue);
     }
     """
     )
webio_serve(page("/", req -> s), 8000)
obs[] = "22"

Then the web console prints out the value 22.

answered Mar 30, 2022 at 9:44

Oskar

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3 Comments

Rodrigo Vargas Over a year ago

Thank you so much! Just to make it easier for casual readers: the difference is that we are passing the observable obs to onjs, instead of the scope and the observable's name.

Rodrigo Vargas Over a year ago

Just discovered: one can also write s[:logme] instead of obs, which might be useful if a reference to the observable is not readily available.

Oskar Over a year ago

Yes, I could have made it more clear. The information about the scope is already in the observable and onjs(obs, [...]) calls onjs(s, "logme", [...]), but it also calls the ensure_sync before.

Ranjith Raina · Accepted Answer · 2022-03-30 10:21:48Z

0

Try this It will helps

WebIO.webio_serve( page("/", req -> s) )

answered Mar 30, 2022 at 10:21

Ranjith Raina

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