rounding numbers: Metric-imperial measurements conversion calculator / scrimba project

Question

I'm pretty much finished with a conversion calculator project from scrimba, but have had no success with rounding number to 3 decimals.

I have played around with math.round/math.floor with no success. Any suggestions would be appreciated!

Here is a snippet of my work:

let feetOutput = document.getElementById("feet-output");
let meterOutput = document.getElementById("meter-output");
meterInput = document.getElementById("meter-input");
let mainInput = document.getElementById("main-input");
litterInput = document.getElementById("litter-input")
feetInput = document.getElementById("feet-input");

document.getElementById("main-Input").value = '';
document.getElementById("main-Input").textContent = 0;

function lengthConverter(valNum) {

  document.getElementById("feet-output").innerHTML = valNum * 3.281 + " Feet";
  document.getElementById("meter-output").innerHTML = valNum / 3.281 + " meters";
  document.getElementById("gallons-output").innerHTML = valNum / 3.785 + " gallons";
  document.getElementById("litter-output").innerHTML = valNum * 3.785 + " liters";
  document.getElementById("pounds-output").innerHTML = valNum * 2.205 +
    " pounds";
  document.getElementById("kg-output").innerHTML = valNum / 2.205 + " kilograms";

}


function lengthConvertermf(valNum) {
  document.getElementById("feet-output").innerHTML = roundedUp((((valNum * 10) * (3.281 * 10)) / 10) * 1000 / 1000 + " Feet");

}


function lengthConverterfm(valNum) {
  document.getElementById("meter-output").innerHTML = (((((valNum * 10) / (3.281 * 10) / 10) * 1000) / 1000) + " meters");
  Math.round((num + Number.EPSILON) * 100) / 100
}

function lengthConverterlg(valNum) {
  document.getElementById("gallons-output").innerHTML = roundedUp(valNum / 3.785 + " gallons");
}

function lengthConvertergl(valNum) {
  document.getElementById("litter-output").innerHTML = roundedUp(valNum * 3.785 + " liters");
}

function lengthConverterkp(valNum) {
  document.getElementById("pounds-output").innerHTML = roundedUp(valNum * 2.205) +
    " pounds";
}

function lengthConverterpk(valNum) {
  document.getElementById("kg-output").innerHTML = roundedUp(valNum / 2.205 + " kilograms");
}

Answer 1

const round = (num, n) => Number.parseFloat(num.toFixed(n));
//using:
console.log(round(3.14159, 3));

const floor = (num, n) => Number.parseFloat(num.toFixed(n)) - Math.pow(10, -n);