function sum(a) {
var sum = a
function f(b) {
sum += b
return f
}
f.toString = function () { return sum }
return f
}
var a = sum(0)(1)(2)(3)(4)(5);
Can someone explain to me how does this code works? I really don't get how to call function with multiple closures in such a way. And why when i print a in the browsers console the result is "function 15" and not just 15
And why when i print a in the browsers console the result is "function 15" and not just 15
To get final result you should call toString function. This closure holds the sum until you call toString function.
function sum(a) {
var sum = a
function f(b) {
sum += b
return f
}
f.toString = function() {
return sum;
}
return f
}
var a = sum(0)(1)(2)(3)(4)(5);
document.write(a.toString());sum(0) returns a function f that closes over the local variable sum (the only closure in that code). Because it returns a function it means you can call that function which also accepts an argument and returns itself which is how you can keep chaining like that.
sum(0) // `sum` is 0, returns f (a function)
sum(0)(1) // returns f which adds 1 to `sum` and returns f again
// and again etc
Another way of thinking about it:
var fn0 = sum(0) // `sum` is 0, returns f (a function)
var fn1 = fn0(1) // returns f which adds 1 to `sum` and returns f again
var fn2 = fn1(2) // ...
return f)