The Fibonacci sequence in JavaScript: how my implementation is 161% faster.

fibonacci.js

// This code is the companion for my article:
// "Program performance: cleaner !== better"
// You can read it here:
// https://www.infinium.earth/article/program-performance

// How many interations each function is
// called to check the average.
const ITERATIONS = 100;

const BASE_N = 200;

const average = a => a.reduce((t, c) => t + c) / a.length;

// My implementation:
const myFib = (n) => {
	let res = [];
    
    // Using a while-loop here was ever so
    // slightly slower.
    
    // Moreover, using a ternary operator was
    // slightly slower.

	for (let i = 0; i < n; ++i) {
		let v;
		
		if (i > 1) {
			v = res[i - 1] + res[i - 2];
		} else {
			v = i;
		}
		
		res.push(v);
	}

	return res;
}

// Their solution:
const theirFib = n => {
	return Array.from({ length: n }).reduce(
		(acc, val, i) => acc.concat(i > 1 ? acc[i - 1] + acc[i - 2] : i),
		[]
	);
}

const checkAverage = (f) => {
	let s1 = [];
	
	for (let i = 0; i < ITERATIONS; ++i) {		
		const t0 = performance.now();
		
		f(BASE_N);
		
		const t1 = performance.now();
		
		s1.push(t1 - t0);
	}
	
	return `${average(s1)} - ${f.name}`
};

console.log(checkAverage(myFib));
console.log(checkAverage(theirFib));