Question

I am trying to write an adapter for a client-side HTML/JS templating system to use dust.js under the hood. Unfortunately the API expects render operations to occur synchronously: the rendered output should be returned from the render() call. Dust.js is asynchronous and passes render output to a callback function. Is there any way to work around this, either in the Dust APIs or through some crazy Javascript hack?

Answer 1

DustJS is only going to execute things asynchronously when the resources it needs to render (templates, partials) haven’t already all been loaded.

If all the dependencies of a template are loaded before you execute that template then it’ll execute synchronously (as far as I can tell anyhow). So you can do something like:

var result;
dust.render("tpl", data, function(err, res) {
   result = res;
});
console.log(result); // result will actually already be filled out if dustjs didn't
// have to go look for resources somewhere.

Here is a fuller example below:
(and here is a jsfiddle link so you can run it: http://jsfiddle.net/uzTrv/1/)

<script type="text/javascript" src="dust.js"></script>
<script>
    var tpl = dust.compile("Omg {#people} {.} {/people} are here! {>partial/}", "tpl");
    var partial = dust.compile("I'm a partial but I've already been included so things still run {how}", "partial");
    dust.loadSource(tpl);
    dust.loadSource(partial);

    var data = {
        people: ["jim", "jane", "jack", "julie"],
        how: "synchronously!"
    };

    var result;
    dust.render("tpl", data, function(err, res) { 
        result = res;
    });
    console.log(result);
</script>

There could be cases (besides the one I mentioned) where I’m wrong… I don’t know everything about dustjs.