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JavaScript JavaScript Basics (Retired) Working With Numbers The Mad Libs Challenge Revisited

Posted by Maneesh Kumar
Maneesh Kumar
Courses Plus Student 321 Points

How do we print out just the decimal part of a float value?

Eg. I want to print out .15 in 273.15 .

3 Answers

miikis
miikis
44,957 Points

Hey Maneesh,

The easiest, and most practical, method to accomplish this task is the modulo operator. It's rendered as the percentage sign (%) and it works like this.

var num1 = 100, num2 = 7;

var answer = 100 / 7; // returns 14.28571429
var remainder = 100 % 7; // returns 2

So, if you're just trying to get the last 2 digits of a float, you could use some String method (like slice). But more than likely, you're trying to find the remainder... and that's what the modulo operator does. Let me know if that answers your question.

Maneesh Kumar
Maneesh Kumar
Courses Plus Student 321 Points

First of all thanks for answering and abiut the answer, i am looking for a way to seperate the decimal part from the whole number part.Like in your answer above i want the .2857... part separated from the returned answer so it reads something like 100/7 = 14 + .2857....

miikis
miikis
44,957 Points

Gotcha. Well, take a look at this then:

var num1 = 100, num2 = 7;

var answer = 100 / 7; // returns 14.28571429

var decimalPart = answer - Math.floor(answer); //Basically, 14.28571429 - 14... which returns (.28571429)

var onlyTwoDecimalPlaces = decimalPart.toFixed(2); //This toFixed method converts a Number into a String and keeps only the specified number of decimals

Is that more helpful?

Maneesh Kumar
Maneesh Kumar
Courses Plus Student 321 Points

Sure is, thanks Mr. Woodwinter.

Robert Richey
PLUS
Robert Richey
Courses Plus Student 16,352 Points
Robert Richey
Robert Richey
Courses Plus Student 16,352 Points

Hi Maneesh,

// note: this is a number and not a string
var float = 273.15;

// let's get the position of the radix-point
var radixPos = String(float).indexOf('.');

// now we can use slice, on a String, to get '.15'
var value = String(float).slice(radixPos);

console.log(value); // '.15'

Cheers

Maneesh Kumar
Maneesh Kumar
Courses Plus Student 321 Points

Thanks for the help bud but this stuff just flew over my head.

Robert Richey
PLUS
Robert Richey
Courses Plus Student 16,352 Points
Robert Richey
Robert Richey
Courses Plus Student 16,352 Points

Hmm, for now feel free to use the function below. Call the function with any number you want to extract the mantissa - including the radix point - which is called a decimal point when values are base 10.

I do apologize if it seems like I'm over-complicating this - I'm not trying to. I'll be more than happy to try and answer any specific questions you may have. If none of this makes sense, I wouldn't know where to begin.

function getFraction(n) {
  var s = String(n);
  return s.slice(s.indexOf('.'));
}

// example usage
var number = 273.15;
console.log(getFraction(number));  // output: '.15'

// another example
var pi = 3.14159265359;
console.log(getFraction(pi));  // output: '.14159265359'

All the best,

Robert

Maneesh Kumar
Maneesh Kumar
Courses Plus Student 321 Points

OK got this one, thanks for the help.