CODEWITHSUNDEEP
javascript
John John
John John

Reputation: 1500

Multiple arguments composible function implementation using reduceRight()

I am trying to re-implement function composition using reduceRight. Here is a function composition that I am trying to re-implement:

const compose = function([func1, func2, func3]) {
  return function(value1, value2) {
    return func1(func2(func3(value1, value2)));
  };
};

const func3 = (x, y) => {
  return y > 0 ? x + 3 : x - 3;
};

const func2 = x => {
  return x ** 2;
};

const func1 = x => {
  return x - 8;
};

const fn = compose([func1, func2, func3]);

console.log(fn('3', 1)); // 1081
console.log(fn('3', -1)); // -8

The following code is re-implementation of the above function. It looks like the argument y is getting undefined I am not sure why.

const compose = (...args) => value =>
  args.reduceRight((acc, fn) => fn(acc), value);

const func3 = (x, y) => {
  return y > 0 ? x + 3 : x - 3;
};

const func2 = x => {
  return x ** 2;
};

const func1 = x => {
  return x - 8;
};

const fnOne = compose(
  func1,
  func2,
  func3
)('3', 1);
console.log(fnOne);//-8

const fnTwo = compose(
  func1,
  func2,
  func3
)('3', -1);
console.log(fnTwo);//-8

Upvotes: 2

Views: 182

Answers (1)

adiga
adiga

Reputation: 35253

Similar to compose, you could use rest parameter syntax get an an array of values. Then destructure the func3 arguments to get x and y like this:

const compose = (...args) => (...values) =>
  args.reduceRight((acc, fn) => fn(acc), values);

// an array of values is passed here
// destructure to get the x and y values
const func3 = ([x, y]) => y > 0 ? x + 3 : x - 3;

const func2 = x => x ** 2;

const func1 = x =>  x - 8;

const fnOne = compose(
  func1,
  func2,
  func3
)('3', 1);
console.log(fnOne);//1081

const fnTwo = compose(
  func1,
  func2,
  func3
)('3', -1);
console.log(fnTwo);//-8

Upvotes: 1

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