# Performance.now() Function

Question:
I am making a Dice Roller program to see how long it takes to roll an amount of dice with an amount of sides. To start a timer I am using the `performance.now()` function but it doesn’t work, it says it’s not a function.

``````var performance = require("performance");

function randInt(min, max) {
return Math.floor(Math.random() * (max - min + 1)) + min
}

let dieAmount = prompt("Amount of Dice ")
let dieSides = prompt("Amount of Sides on a Die ")
dieSides = parseInt(dieSides)
dieAmount = parseInt(dieAmount)

let rolledCorrectly = false

let startTime = performance.now()

while (!rolledCorrectly) {
const rolls = []

for (let i = 0; i < dieAmount; i++) {
let currentRoll = randInt(1, dieSides)
rolls.push(currentRoll)
}

let allSame = true;
for (let j = 1; j < rolls.length; j++) {
if (rolls[0] !== rolls[j]) {
allSame = false
break
}
}

if (allSame) {
rolledCorrectly = true
}
}

let endTime = performance.now()

let totalTime = (startTime - endTime) / 1000

console.log('Successfully rolled the same number on all dice! It took \${totalTime} seconds')
``````

No, why… You know what `const` is…

Anyway do this

``````const { performance } = require("performance");
``````

@QwertyQwerty88 I didn’t know how to import modules on JS so I looked it up (Im pretty new to JS), I do know how to use `const`’s for lists though. It does through another error though `TypeError: Cannot read properties of undefined (reading ‘now’)`.

I don’t think your Node version is high enough for `performance`. Otherwise Idk what’s going on.

``````const { performance } = require("perf_hooks");
``````
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Careful there, make sure you are using backticks, or it will raise an error. I’m guessing you’ve probably fixed this already.

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