webworker-threads/examples/ex01_basic.js

Lightweight Web Worker API implementation with native threads

/// !example
/// ## 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('webworker-threads');
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:
t.eval(fibo);
/// 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
	step2();
});
/// Let's call it again:
function step2() {
	t.eval('fibo(20)', function(err, result) {
		if (err) throw err;
		console.log('fibo(20)=' + result);
		step3();
	});
}
/// 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);
		step4();
	});
}
/// 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);
		step5();
	});
}
/// Once we are done, we destroy the thread:
function step5() {
	t.destroy();
}
/// ### Output
/// 
/// ```
/// fibo(10)=89
/// fibo(20)=10946
/// error=Error: ReferenceError: x is not defined
/// fibo(15)=987
/// ```