vimwiki/lang/Node.js.wiki

= Node.js =

Node.js is an Asynchronus, event driven javascript runtime. On line the command
is `node`.

== Hello World ==

1) Create a file called `index.js`. This is always the entry point (similar to
   a main()).
2) Place code. It is interpreted the same as if it were in the browser. For
   example, 
   {{{
       console.log("hello world")
    }}}
   
== Events ==

Events are times when certain things happen. We can do things on those events
by using a callback. This is accessed via the process object. For example,

{{{
    process.on('exit', function() {
        Console.log("Goodbye!");
            });
  }}}
  
Will print goodbye to the console when the program terminates. process.on takes
two paramaters, the event name '`exit`', and the function (or lambda).

To create an event, we can use the Event Emitter, a node.js builtin. The
following example is an annotated example of exactly that.

{{{
//pull in the event emitter dependency
const { EventEmitter } = require('events');

//create the event emitter
const eventEmitter = new EventEmitter();

//create the callback 'lunch'
eventEmitter.on('lunch', function() {
    console.log("Lunch time");
        });
        
//trigger the callback function
eventEmitter.emit('lunch');
  }}}
  
As you can see, this is a similar concept to something like function pointers,
where a pointer is assigned then later called through the pointer.

== File system ==

The file system can be read in two modes, either in a block or non blocking
mode (similar to async calls in C#)