An Example

Suppose we want to write a function that calculates the sum of all numbers from 1 up to (and including) some number n.

function addUpTo(n){
	let total = 0; //total is also called accumulator
	for(let i = 0;i <= n;i++){
		total += i;
	}	
	return total;
}

function addUpTo(n){
	return n * (n + 1) /2;
}

                                               Which one is better ?

Actually What does better mean?

• Faster ?
• Less memory-intensive ?
• More readable ?

To know the time or which is faster

                                         Why not use timers?

function addUpTo(n){
	let total = 0; 
	for(let i = 0;i <= n;i++){
		total += i;
	}	
	return total;
}

let t1 = performance.now();
addUpTo(1000000000);
let t2 = performance.now();
console.log(`Time Elapsed: ${(t2-t1) / 1000} seconds.`);

The Problem with Time

• Different Machines will record different times
• The same machine will record different times!
• For fast algorithms, speed measurements may not be precise enough?