JavaScript中具有多个参数的功能

Question

I just received this test

function darling(w) {
/**
 * your code here
 */
}

/**
 * test functions, those in comment are expected returned value
 */
var demoIsWorking = demo();
var absolutely = darling('w')('i')('l')('l')['y']['o']['u'].m.a.r.r.y('m').e['?'];
var definitely = darling('w')('o')('u')('l')('d')['y']['o']['u'].m.a.r.r.y('m').e['?'];
var rUKidding = darling('w')('i')('l')('l')['y']['o']['u'].m.a.r.r.y('h').im['?'];
var yNot = darling('w')('o')('u')('l')('d')['y']['o']['u'].m.a.r.r.y('h').im['?']; 

As you can see from the code when the program call a function darling, it's has many different parameters with different () and []. It's really make me confuse. Can someone explain for me why the function is possible to have many parameters and also many bracket.

Thanks for your help

Answer 1

A function can return anything, for example an object or another function. For example:

function matchesYou() {
  return { y: { o: { u: true } } };
}

Makes the following possible:

matchesYou().y.o.u;

Which you can also write as:

matchesYou()['y']['o']['u'];

Or any combination of both.

For round parentheses, it's even simpler:

function darling(w) {
  return function(iOrU) {
    return function(lOrU) {
      return function(l) {
        return true;
      };
    };
  };
}

You can call that like this:

darling('w')('i')('l')('l');

Or like this, it doesn't matter:

darling()()()();

Answer 2

There is only one argument being passed at most.

What it's doing is it's actually doing chaining different functions by having a function return another.

function someFunction(w) {
  switch(w): {
    case 'a':
      return function() { ... }
    case 'b':
      return function() { ... }
  }
}

calling someFunction may return a completely different function depending on the argument passed.

Somewhere within those functions, it returns an array within an array

[
  ['a','b','c'],
  ['a','b','c'],
  ['a','b','c'],
];

Some of which containing objects

[{a:'1',b:'2' ....}], 'b']