Format number without rounding, limitimg decimal places, operate futher on number-CodePudding

I`d like to format decimal number 0.0003333333333333333 to 0.00033 without rounding. Number is coming from division decimal numbers. Also want to operate futher with number 0.00033.

toFixed(), Math.round(), toPrecision() are rounding so im not keeping eye on it.

I was thinking about parsing number to string, use slice and next parse text to number again.

Code:

let salesMixOld1 = document.querySelector("#sales-mix-old-1");
let cosOldPromo = document.querySelector("#cos-old-promo");
let salesMixOld2 = document.querySelector("#sales-mix-old-2");

let daysInMonth = document.querySelector("#days-in-month");
let howMuchDaysPromotion = document.querySelector("#how-much-days-promotion");

const calculateCosAll = () => {
    let parseCosAll = parseFloat(cosAll.value);
    let parseSalesMixOld1 = parseFloat(salesMixOld1.value);
    let parseCosOldPromo = parseFloat(cosOldPromo.value);
    let parseSalesMixOld2 = parseFloat(salesMixOld2.value);

    let resultCalculateCosAll = (parseCosAll - (parseCosOldPromo * parseSalesMixOld2)) / parseSalesMixOld1;

    calculatedCosAllDiv.innerHTML = resultCalculateCosAll;
}

const calculateSalesMixPerDay = () => {
    let parseSalesMixOld2 = parseFloat(salesMixOld2.value);
    let parsedaysInMonth = parseFloat(daysInMonth.value);
    let parsehowMuchDaysPromotion = parseFloat(howMuchDaysPromotion.value);

    let resultCalculateSalesMixMonth = parseSalesMixOld2 / parsedaysInMonth;
    let resultCalculateSalesMixDay = resultCalculateSalesMixMonth * parsehowMuchDaysPromotion;

    calculatedSalesMixDiv.innerHTML = resultCalculateSalesMixMonth   "/"   resultCalculateSalesMixDay;
}


calculateCosAllBtn.addEventListener('click', calculateCosAll);
calculateSalesMixBtn.addEventListener('click', calculateSalesMixPerDay);

CodePudding user response：

To avoid rounding you can multiply by the appropriate power of 10, call Math.trunc() which will return the integer part of a number discarding the decimal, and then divide again.

const input = 0.000338;
const result = Math.trunc(input * 100_000) / 100_000;

console.log(result);

Or as a helper function

function truncate(number, places) {
  return Math.trunc(number * 10 ** places) / 10 ** places;
}

const input = 0.000338;
console.log(truncate(input, 5));

CodePudding user response：

Like this one ?

const num2precise = (num, decimals = 5) =>
  {
  let 
    s = num.toString()
  , p = s.indexOf('.')
    ;
  s  = (p<0 ? (p=1 s.length, '.'):'')   '0'.repeat(decimals)
  return s.slice(0,p 1 decimals )
  }

console.log( num2precise( 0.0003333333333333333 )) //  0.00033
console.log( num2precise( 0.000339 ))              //  0.00033
console.log( num2precise( 0.0003 ))                //  0.00030
console.log( num2precise( 25 ))                    // 25.00000
console.log( num2precise( 25, 7 ))                 // 25.0000000

if you prefer a Number value :

const num2precise = (num, decimals = 5) =>
  {
  let 
    s = num.toString()
  , p = s.indexOf('.')
    ;
  return Number( (p<0) ? s : s.slice(0,p 1 decimals))
  }

console.log( num2precise( 0.0003333333333333333 )) //  0.00033
console.log( num2precise( 0.000339 ))              //  0.00033
console.log( num2precise( 0.0003 ))                //  0.0003 
console.log( num2precise( 25 ))                    // 25

CodePudding user response：

let number = 0.0003333333333333333;
Number(number).toFixed(4);
console.log(Number(number).toFixed(5));
//result 0.00033