2629-function-composition.js

/**
 * @param {Function[]} functions
 * @return {Function}
 */
var compose = function(functions) {
	return function(x) {
        let result = x;
    for (let i = functions.length - 1; i >= 0; i--) {
      result = functions[i](result);
      // console.log(result);
    }
    return result;
    }
};

/**
 * const fn = compose([x => x + 1, x => 2 * x])
 * fn(4) // 9
 */