How to remove digits after decimal using JavaScript?

Question

I am using numeric in an HTML web page. The problem is that I want numbers without decimals.

function copyText() {
  var mynumber = document.getElementById("field1").value;
  alert(mynumber);
  var mytest = parseInt(mynumber);
}

Field1: <input type="number" id="field1" value="123.124" /><br /><br />
<button onclick="copyText()">Check Number</button>

<p>A function is triggered when the button is clicked. The function copies the text in Field1 to Field2.</p>

possible duplicate of How do I convert a float to an int in Javascript? — user1233508
– user1233508, Commented Sep 14, 2012 at 11:47
When you say "still does not work" it would be more informative to tell what you get - error or worng value or what? — mplungjan
– mplungjan, Commented Sep 14, 2012 at 12:05
You're first question was about multiplying floating point numbers with integers, and now it's about parsing strings, making some of these answers irrelevant. — Aesthete
– Aesthete, Commented Sep 14, 2012 at 12:51

vzwick · Accepted Answer · 2017-10-10 19:25:19Z

24

Assuming you just want to truncate the decimal part (no rounding), here's a shorter (and less expensive) alternative to parseInt() or Math.floor():

var number = 1.23;
var nodecimals = number | 0; // => 1

Further examples for the bitwise OR 0 behavior with int, float and string input:

10     | 0 // => 10
10.001 | 0 // => 10
10.991 | 0 // => 10
"10"   | 0 // => 10
"10.1" | 0 // => 10
"10.9" | 0 // => 10

edited Oct 10, 2017 at 19:25

answered Sep 14, 2012 at 11:40

vzwick

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6 Comments

Aesthete Over a year ago

Should we really assume that speed is an issue an an operation like this? It's faster than floor because floor handles multiple types. Floor is also explicit in it's intentions. Novel approach though, +1.

Shahzad CR7 Over a year ago

check how to change that in function

vzwick Over a year ago

@Aesthete "Floor handles multiple types" – so does the bitwise OR 0: 10|0 => 10, 10.1|0 => 10, "10"|0 => 10, "10.1"|0 => 10 … Semantically, floor() is better suited, of course.

vzwick Over a year ago

@Jake - Thanks for pointing this out. The problem isn't in the approach per se, but due to floating point arithmetics: 2.3 * 100 = 229.99999999999997. I added a disclaimer to the answer nonetheless.

James Wilkins Over a year ago

@Jake This issue can easily be solved for some cases by adding a SMALL fraction to give a little "push" to numbers - assuming you're only dealing with positive numbers. For example, ((2.3+0.00000000001)*100)|0 === 230 just fine. For all others it simply adds such a small amount that nothing much happens. I'm building a simulation engine where speed is important, and which does not need perfect precision, and I think this works great for my needs. ;)

|

John Conde · Accepted Answer · 2012-09-14 11:39:15Z

9

You should use JavaScript's parseInt()

answered Sep 14, 2012 at 11:39

John Conde

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2 Comments

David Thomas Over a year ago

He already is; albeit he's not using the radix for some reason...though I'm curious as to why he hasn't simply re-used parseInt().

vzwick Over a year ago

@Jake - parseInt works as intended. It's 2.3 * 100 that doesn't yield what you would expect.

ALLSYED · Accepted Answer · 2016-07-29 12:30:05Z

5

In ES6 , you can use builtin method trunc from Math Object

 Math.trunc(345.99933)

answered Jul 29, 2016 at 12:30

ALLSYED

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Comments

g1ji · Accepted Answer · 2016-11-24 11:48:16Z

4

var num = 233.256;
console.log(num.toFixed(0));

//output 233

answered Nov 24, 2016 at 11:48

g1ji

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1 Comment

Zied Hf Over a year ago

Don't use this. 233.9.toFixed(0) returns 234 not 233.

Jakub Konecki · Accepted Answer · 2012-09-14 11:38:52Z

2

returns string:

(.17*parseInt(prescription.values)*parseInt(cost.value)).toFixed(0);

returns integer:

Math.round(.17*parseInt(prescription.values)*parseInt(cost.value));

Remember to use radix when parsing ints:

parseInt(cost.value, 10)

answered Sep 14, 2012 at 11:38

Jakub Konecki

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1 Comment

RobG Over a year ago

toFixed has various issues (e.g. (0.595).toFixed(2) gives 0.59 in Firefox, 0.60 in IE), better to use Math.round or similar.

Aesthete · Accepted Answer · 2012-09-14 11:40:40Z

1

Mathematically, using a floor function makes the most sense. This gives you a real number to the largest previous integer.

ans7 = Math.floor(.17*parseInt(prescription.values)*parseInt(cost.value));

answered Sep 14, 2012 at 11:40

Aesthete

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5 Comments

Shahzad CR7 Over a year ago

still not working for me basically i am setting these value on graph bar

Shahzad CR7 Over a year ago

basically prescript.values is text type field not number i think that may be the issue

Aesthete Over a year ago

@ShahzadBaloch - Are you sure it's because you're looking for one property called value and the other called values? If either of these values is undefined you're going to get NaN returned. Otherwise is you multiple a float by two ints and floor the result it will always work.

mplungjan Over a year ago

And add a radix ans7 = Math.floor(.17*parseInt(prescription.value,10)*parseInt(cost.value,10));

Shahzad CR7 Over a year ago

i have added code how to change that num value to withoud decimal

Jignesh Rajput · Accepted Answer · 2012-09-14 11:40:35Z

0

Have you try to get value using parseInt

Try :

console.log(parseInt(ans7));

answered Sep 14, 2012 at 11:40

Jignesh Rajput

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Comments

Penny Liu · Accepted Answer · 2020-10-27 15:10:08Z

0

~~ operator is a faster substitute for Math.floor().

function copyText() {
  var mynumber = document.getElementById("field1").value;
  alert(~~mynumber);
}

<fieldset>
  <legend>Field1</legend>
  <input type="number" id="field1" value="123.124" />
  <button onclick="copyText()">Check Number</button>
</fieldset>

edited Oct 27, 2020 at 15:10

answered Apr 27, 2020 at 6:49

Penny Liu

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