task.js

by Dave Herman

• What? Cooperative concurrency for JS + generators.
• Why? Who says JavaScript I/O has to be ugly?
• Where? http://dherman.github.com/taskjs
• How? http://dherman.github.com/taskjs/doc/api.html

task.js provides an automatic task scheduler along with a library of first-class, synchronizable events, making it easy to do I/O without callbacks.

task.js lets you write this code:

spawn(function() {
    try {
        var [foo, bar] = yield join(read("foo.json"),
                                    read("bar.json")).timeout(1000);
        render(foo);
        render(bar);
    } catch (e) {
        console.log("read failed: " + e);
    }
});

instead of, say, this code:

var foo, bar;
var tid = setTimeout(function() { failure(new Error("timed out")) }, 1000);

var xhr1 = makeXHR("foo.json",
                   function(txt) { foo = txt; success() },
                   function(err) { failure() });
var xhr2 = makeXHR("bar.json",
                   function(txt) { bar = txt; success() },
                   function(e) { failure(e) });

function success() {
    if (typeof foo === "string" && typeof bar === "string") {
        cancelTimeout(tid);
        xhr1 = null;
        xhr2 = null;
        render(foo);
        render(bar);
    }
}

function failure(e) {
    xhr1 && xhr1.abort();
    xhr1 = null;
    xhr2 && xhr2.abort();
    xhr2 = null;
    console.log("read failed: " + e);
}