javascript two brackets after function name

Question

What does below syntax means?

connect(mapStateToProps, mapDispatchToProps)(Home)

I understand we are passing two arguments to a function, but what is the purpose of below one?

(Home) 

Answer 1

It doesn't look like node but Redux and as in a comment not an ES6 thing.

What it is: Connect is a higher order (factory) function ie. it returns a function. And it is that returned function which is immediately called with Home

Take a look and an example of mock of connect below

function connect(param1, param2) {
    return innerFunction (innerParam) {
       console.log(`${param1} ${innerParam} ${param2}`) 
    }
}

connect('A','B')('precedes')

// outputs 'A precedes B'

Edit: Added an example.

Answer 2

A function can return a function, and you can call this returned function immediately.

For information and as already stated in comments, the fact of decomposing one function call into smaller like this one in your example is called currying and is a common practice in JavaScript (more info here : What is 'Currying'?)

This example might help you :

function function1(info) {
    return function(innerParam) {
        console.log(`Hello this function has info ${info} and has just been called with this param: ${innerParam}` )
    }
}

function1('Bobby')('Alice');

// same as :
var bobbyFunction = function1('Bobby');
bobbyFunction('Alice');

This is useful to dynamically generate a function that depends on some parameter, but can still be called several time with some other changing parameters. Imagine this, for instance :

var bobbyFunction = function1('Bobby');
['Alice', 'Tommy', 'Johny'].forEach(name => bobbyFunction(name));

Answer 3

It's plain javascript. Function connect returns another function and code immediately calls it with parameter Home.

function first(f) {
  return function second(s) {
    console.log(f, s);
  }
}

// this
first('one')('two');

// is same as this
var x = first('one');
x('two');

Answer 4

see this example:

connect(mapStateToProps, mapDispatchToProps)(Home)// just like code below

function f(){
    //do something
}
function connect(a,b){
    return f;
}

connect(mapStateToProps, mapDispatchToProps);//first,return f;

connect(mapStateToProps, mapDispatchToProps)(Home)//second,return f(home);