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ab01f72 Mar 10, 2012
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Running a simple function in a thread

This first example demonstrates how you can run an expensive computation in a worker thread and obtain its result.

First, we define the function that we want to execute in the worker thread:

function fibo(n) {
    return n > 1 ? fibo(n - 1) + fibo(n - 2) : 1;

Then, we create a worker thread with the Threads.create call:

var Threads = require('threads_a_gogo');
var t = Threads.create();

In the next step, we load the function into the worker thead. We get the function's source with fibo.toString() and we call t.eval(source) to evalutate it into the worker thread's context:


Now, we are ready to call this function. We use the t.eval function again, with two arguments this time.
The first argument is the expression to evaluate.
The second one is a callback that receives the result (or an error if there was one).

t.eval('fibo(10)', function(err, result) {
    if (err) throw err; // something abnormal
    // print the result
    console.log('fibo(10)=' + result);
    // chain with next step

Let's call it again:

function step2() {
    t.eval('fibo(20)', function(err, result) {
        if (err) throw err;
        console.log('fibo(20)=' + result);

If the expression is invalid, we get an error through the callback

function step3() {
    // 'x' is not defined
    t.eval('fibo(x)', function(err, result) {
        console.log('error=' + err);

But the thread is still alive and ready to accept more calls:

function step4() {
    t.eval('fibo(15)', function(err, result) {
        console.log('fibo(15)=' + result);

Once we are done, we destroy the thread:

function step5() {


error=Error: ReferenceError: x is not defined