CODEWITHSUNDEEP
javascriptcurryingarrow-functions
Schwafa
Schwafa

Reputation: 167

How can I access the result from a previous function in a currying function?

I have to write a currying function that takes a function, executes another function, then executes a second function by taking the last argument as the value to calculate with.

What I am struggling with: How can I access the first function and the value at the end at the same time?

So far I can access the first function by writing a function in the function syntax and accessing the this. 

Function.prototype.foo = function(x) {
  // can't make currying functions by using functions keyword
  console.log(this, x);
};

(() => 10).foo(1);

When I write a currying function I can access the second (x) and third (y) function.

Function.prototype.bar = x => y => {
  // but also can't access this like in function syntax
  console.log(x, y);
}

// how would I access 10 in bar?
(() => 10).bar(1)(2);

The final Function would look something like that:

someFunc.then(someSecondFunc).then(someThirdFunc)(100)

Thank you so much for your help!

Upvotes: 1

Views: 62

Answers (2)

Schwafa
Schwafa

Reputation: 167

By using currying functions and the function keyword, my answer looks like this:

Function.prototype.then = function(secondFct) {
  const firstFct = this;
  return function(value) {
    return firstFct(secondFct(value));
  }
}

Many thanks to buboh for the help.

Upvotes: 0

buboh
buboh

Reputation: 957

Not sure if it solves your problem, but you can make currying functions with the function keyword:

Function.prototype.bar = function(x) {
    return function(y) {
        console.log(x, y)
    }
}

I wasn’t able to actually able to validate if this works: 

(function() {return 10}).bar(1)(2)

In any case, ˋthisˋ would be the function, not the return value (10), since the function is not called.

Upvotes: 1

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