Asynchronous output

Javascript and Node.JS make heavy use of asynchronous execution. IJavascript lets you exercise these asynchronous capabilities, both:

by updating stdout and stderr asynchronously, or
by updating the IJavascript output asynchronously.

Updating `stdout` and `stderr` asynchronously

Both streams stdout and stderr can be written asynchronously. Any text written to these streams will be forwarded back to the latest request from the frontend:



In [1]:

    
function countTo(number, milliseconds) {
    var counter = function() {
        console.log(counter._n++);
        
        if (counter._n > number) {
            clearInterval(counter._intervalObject);
            console.warn("Done!");
        }
    };
    counter._n = 1;
    counter._intervalObject = setInterval(counter, milliseconds);
}

countTo(5, 1000);









    Out[1]:




undefined






    



1
2
3
4
5






    



Done!

Updating the IJavascript output asynchronously

IJavascript offers two global definitions to help produce an output asynchronously: $$async$$ and $$done$$().

When $$async$$ is set to true, the IJavascript kernel is instructed not to produce an output. Instead, an output can be produced by calling $$done$$().



In [2]:

    
$$async$$ = true;

console.log("Hello!");

setTimeout(
    function() {
        $$done$$("And good bye!");
    },
    1000
);









    



Hello!






    Out[2]:




'And good bye!'

It is also possible to produce a graphical output asynchronously, the same way it is done synchronously, with the difference that $$done$$() has to be called to instruct the IJavascript kernel that the output is ready:



In [3]:

    
$$async$$ = true;

console.log("Hello!");

setTimeout(
    function() {
        $$svg$$ = "<svg><circle cx='30px' cy='30px' r='20px'/></svg>";
        $$done$$();
    },
    1000
);









    



Hello!






    Out[3]:

Asynchronous output

Updating stdout and stderr asynchronously

Updating the IJavascript output asynchronously

Updating `stdout` and `stderr` asynchronously