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I read that the javascript language has characteristics that assist in the implementation of non-blocking IO which contributes to the success of projects like node.js. My question is what are these characteristics and why is non-blocking IO trickier to implement in other languages?
The reason that javascript is sometimes labeled as a non-blocking IO is because of the concept of anonymously defined, (event based), functions. Node.js specifically labels this as their reasoning why javascript is a good server side language. This however, is only a half truth, as it is not technically non-blocking, but it will continue to execute code while waiting for a callback from an anonymous callback/ajax function. I’m not sure if this is what you read, but an explanation offered in one Node tutorial is:
“The other method, the one taken by Node and some extremely fast modern servers such as Nginx and Thin, is to use a single non-blocking thread with an event loop. This is where the decision to use JavaScript really shines, since JavaScript was designed to be used in a single threaded event loop-based environment: the browser. JavaScript’s ability to pass around closures makes event-based programming dead simple. You basically just call a function to perform some type of I/O and pass it a callback function and JavaScript automatically creates a closure, making sure that the correct state is preserved even after the calling function has long since gone out of scope.”
source: http://net.tutsplus.com/tutorials/javascript-ajax/this-time-youll-learn-node-js/
In reference to your multithreading tag, Node.js and Javascript are NOT multithreaded, they use a system of closures to preserve state while waiting for a callback. Therefore, they are NOT completely non-blocking. There are plenty of scenarios where blocking can occur, but for most small implementations, a developer will never encounter a blocking situation.
see here for possible info on why node.js is bad: http://teddziuba.com/2011/10/node-js-is-cancer.html (Link broken)
and here for a rebuttle: http://rhyolight.posterous.com/nodejs-is-not-cancer (Link broken)