Are nodejs data-structures thread-safe by design?

Question

Read in a node.js related web document that it is a single threaded server. So it confuses me whether all data structures by default be thread-safe in a node server!

I have multiple call-backs accessing a global object like this :

callback1{
global_var['key'] = val;
}

callback2{
globalv_var['key'] = val;
}

'key' may be same at times and may be different as well. Will the global_var be thread-safe ? callbacks, as intended gets called back as and when something is done, in no particular order.

Answer 1

Node.JS contains a "dispatcher." It accepts web requests and hands them off for asynchronous processing. That dispatcher is single threaded. But the dispatcher spins up a new thread for each task, and quickly hands off the task to the new thread, freeing the dispatcher's thread for servicing a new request.

To the extent that those task threads are kept separate (i.e. they don't modify each other's state), yes, they are threadsafe.

Answer 2

All of the javascript you write for your node.js applocation executes as if it were running in a single thread.

Any multithreading occurs behind the scenes, in the I/O code and in other native modules. So there's no need to worry about the thread safety of any application code, regardless.