convert a negative number to positive without affecting decimal points in js

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I need to convert a negative number to a positive number. My attempt is as below.

Math.abs(-4.0);

It will return 4 as the answer. But I need 4.0 as the answer. Here I don't know the decimal places to be set. For different numbers, there's a different decimal point value. Actually, that will totally depend on the web socket output. According to the input value, the server-side defined different floating points which there's not any pattern according to our requirement.

So in js, is there any better way to handle this without getting decimal places separately?

javascript
3 Answers

As mentioned in other comments, you won't be able to keep the precision. toFixed() is definitely not a solution and this problem has valid case scenarios.

We had to do something similar where teachers would input a grade (90.05) and were expected to keep the same number of decimals for all their students inside of a single gradebook. Teachers grade differently depending of the situation:

Teacher A | Teacher B | Teacher C
   90          90.5       4.95
   80          88.5       3.80
   75          80.0       5.00

One way to solve this, especially if the request comes as a string (from an input, http request, etc.), is to maintain the number as a string and return a string value.

Note that this is a very crude implementation (our implementation is more fail-safe), but the idea is simple:

function absString(n) {
  numberString = n.toString();
  if (numberString[0] === '-') {
    return numberString.substring(1);
  }
  else {
    return numberString;
  }
}

console.log(absString('-1'));
console.log(absString('-2.0'));
console.log(absString('2.0'));
console.log(absString('-0.57'));

user_83169080

You can use the number toFixed method as follows:

var decimalPlaces = 5 // Change this to change the number of decimals

console.log(Math.abs(-4.0).toFixed(decimalPlaces))

user_129845670

If this is for display purposes only you can use the Intl.NumberFormat object to format your value appropriately. Example:

Intl.NumberFormat(
  undefined,
  { signDisplay: 'never', minimumSignificantDigits: 3, maximumSignificantDigits: 20 }
).format(-4.06364635454000); // "4.06364635454"
Intl.NumberFormat(
  undefined,
  { signDisplay: 'never', minimumSignificantDigits: 1, maximumSignificantDigits: 20 }
).format(-4.0); // "4"
Intl.NumberFormat(
  undefined,
  { signDisplay: 'never', style: 'currency', currency: 'EUR' }
).format(-4.06364635454000); // "€4.06"
user_9103280
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