Closure in JavaScript – whats wrong?

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You somehow have to signalize the end of the chain, where you are going to return the result number instead of another function. You have the choice:

  • make it return a function for a fixed number of times – this is the only way to use the syntax like you have it, but it’s boring. Look at @PaulS’ answer for that. You might make the first invocation (func(n)) provide the number for how many arguments sum is curried.
  • return the result under certain circumstances, like when the function is called with no arguments (@PaulS’ second implementation) or with a special value (null in @AmoghTalpallikar’s answer).

  • create a method on the function object that returns the value. valueOf() is suited well because it will be invoked when the function is casted to a primitive value. See it in action:

    function func(x) {
    function ret(y) {
        return func(x+y);
    }
    ret.valueOf = function() {
        return x;
    };
    return ret;
}

func(2) // Function
func(2).valueOf() // 2
func(2)(3) // Function
func(2)(3).valueOf() // 5
func(2)(3)(4)(5)(3) // Function
func(2)(3)(4)(5)(3)+0 // 17

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