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!