Javascript FAB framework on Node.js

Question

I've seen a slide that presented Fab, a node.js framework.

Is this JavaScript?

Could someone explain what is going on in that code?

I'm all lost.

Answer 1

Is plain JavaScript, it is a function chaining pattern.

The first line, ( fab = require("fab") ) includes the fab function and returns a reference to it.

All the subsequent parentheses are function calls, each function invocation returns probably the same function again and again.

The pattern probably looks like this simplified example:

var foo = function (arg) {
  // detect what the argument is
  if (typeof arg == 'function') {
    // do something with arg
    console.log('function: '+arg());
  } else if (arg instanceof RegExp) {
    // arg is a RegExp...
    console.log('A RegExp: '+arg);
  } else if (typeof arg == "string") {
    // arg is a string
    console.log('A string: '+arg);
  }
  return foo; // return a reference to itself
};

(foo)
  (function() { return "Foo "; })
  (/bar/)
  (" baz!");

Outputs:

function: Foo
A RegExp: /bar/
A string: baz!

Answer 2

That's hard to follow indeed; it doesn't really look like Javascript at all...

Anyway, FAB takes advantage of returning a pointer to the function which was called. For example:

function doSomething(str){
  alert(str);
  return arguments.callee;
}

// Alerts 'hi' and then 'there'
doSomething('hi')('there');

Of course you can implement extra conditions, like counting the number of arguments or checking the type of arguments passed in. For example:

function doSomething(){
  if(arguments.length == 1){
    alert(arguments[0])
  } 
  else if(arguments.length == 2){
    alert(arguments[0] + arguments[1]);
  }

  return arguments.callee;
}

doSomething
  ("Hi, 3 + 4 is:")
  (3, 4);

The last example alerts:

> Hi, 3 + 4 is:
> 7