# How to measure efficiency

Dears,
I have two questions: First. How can I reply to `camperbot` text on URL address:
`[http://forum.freecodecamp.org/t/freecodecamp-challenge-guide-return-largest-numbers-in-arrays/16042/7](http://forum.freecodecamp.org/t/freecodecamp-challenge-guide-return-largest-numbers-in-arrays/16042/7)` ? Second: How can I run the efficiency test (javascript) on the above mentioned page? I tried to run it in the FCC javascript console and got following error message: `ReferenceError: require is not defined` . Thank you for help.

What do you mean by running an efficiency test?

I mean running the script:

`````` 1 var Benchmark = require('benchmark');
2 var suite = new Benchmark.Suite;
3
4 function largestOfFourBind(arr) {
5   return arr.map(Function.apply.bind(Math.max, null));
6 }
7
8 function largestOfFourES6(arr) {
9   return arr.map((a) => Math.max(...a));
10 }
11
12 function largestOfFourVanilla(arr) {
13   return arr.map(function(a) {
14     return Math.max.apply(null, a);
15   });
16 }
17
20     largestOfFourBind([[4, 5, 1, 3], [13, 27, 18, 26], [32, 35, 37, 39], [10    00, 1001, 857, 1]]);
21 })
23     largestOfFourES6([[4, 5, 1, 3], [13, 27, 18, 26], [32, 35, 37, 39], [100    0, 1001, 857, 1]]);
24 })
26     largestOfFourVanilla([[4, 5, 1, 3], [13, 27, 18, 26], [32, 35, 37, 39],     [1000, 1001, 857, 1]]);
27 })
29 .on('cycle', function(event) {
30    console.log(String(event.target));
31 })
32 .on('complete', function() {
33    console.log('Fastest is ' + this.filter('fastest').map('name'));
34 })
35 // run async
36 .run({ 'async': true });
``````

from the cited page.

Where are you trying to run this? `require` is a function provided by the NodeJS runtime, it’s not just JS, and it works by making a lookup in the filesystem. If you’re trying to run this on FCC, neither of these things exist, so it can’t work. You run this online using repl.it and using Node on there.

Note the benchmarks won’t tell you anything useful here, sample size is absolutely miniscule, you normally need to run benchmarks on much larger sizes and run them thousands of times