Discussion on: Mastering Hard Parts of JavaScript: Callbacks IV

[Sarratas]

Hi,

Your solution for exercise 20 is not really correct. It works for provided functions and inputs, but won't work for situations where, for example, first function appends something to the string. It also assumes that parameters are strings.

Example where it will fail (return ssss):

const addS = (str) => str + 's';
const addLowerCase = (str) => str + str.toLowerCase();
const repeat = (str) => str + str;
const capAddlowRepeat = [addS, addLowerCase, repeat];
console.log(pipe(capAddlowRepeat, "cat"));

I believe more complete and actually also simpler solution is to correctly use initial value of reduce, like below:

function pipe(callbacks, value) {
  return callbacks.reduce((accum, cb) => cb(accum), value);
}

Cheers!