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#2629 - Function Composition
Problem Description
Given an array of functions [f1, f2, f3, ..., fn], return a new function fn that is the function composition of the array of functions.
The function composition of [f(x), g(x), h(x)] is fn(x) = f(g(h(x))).
The function composition of an empty list of functions is the identity function f(x) = x.
You may assume each function in the array accepts one integer as input and returns one integer as output.
Solution
/**
* @param {Function[]} functions
* @return {Function}
*/
var compose = function(functions) {
return x => functions.reduceRight((result, fn) => fn(result), x);
};