how to make this syntax possible in node.js console (javascript) [duplicate]

Question

The same function summ :

summ(7)(3)(5) must equal 15

and

summ(7)(3)+5 must equal 15

and

summ(7)(3) must equal 10

How to make it possible?

summ should return something that can optionally be treated as either a function or a number...? — deceze
– deceze ♦, Commented Jun 28, 2016 at 10:10

vp_arth · Accepted Answer · 2016-06-28 10:27:16Z

3

You can use toString/valueOf method to treat result as a value.

function sum(a) {
  chain.valueOf = function() {return a;}
  return chain;

  function chain(s) {
    a += s;
    return chain;
  };
}

sum(7)(3)(5)  == 15  // true
sum(7)(3) + 5 == 15  // true
+sum(7)(3)(5)        // 15

edited Jun 28, 2016 at 10:27

answered Jun 28, 2016 at 10:17

vp_arth

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5 Comments

Bergi Over a year ago

valueOf makes more sense for non-string values, though

hear whtti Over a year ago

I've edited my question. Help, please. Thank you!

vp_arth Over a year ago

@hearwhtti, what's wrong? it works. It must to return a function to possibility of next call, but valueOf allow us to interpret this function as a value. +sum(7)(3) === 10, sum(7)(3) == 10. What more you need?

hear whtti Over a year ago

I'm studying, can you, please, explain: why 'sum(7)(3) === 10' returns false and '+sum(7)(3) == 10' returns true. What is purpose of '+' ?

vp_arth Over a year ago

+val is like 0+val just type conversion to numeric. sum(5) result has function type. It's why strict equality === fails. After type conversion with +sum(5) both side has number type and same value.

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