I am looking for an easy way in JavaScript to check if a number has a decimal place in it (in order to determine if it is an integer). For instance,
23 -> OK
5 -> OK
3.5 -> not OK
34.345 -> not OK
if(number is integer) {...}
Using modulus will work:
num % 1 != 0
// 23 % 1 = 0
// 23.5 % 1 = 0.5
Note that this is based on the numerical value of the number, regardless of format. It treats numerical strings containing whole numbers with a fixed decimal point the same as integers:
'10.0' % 1; // returns 0
10 % 1; // returns 0
'10.5' % 1; // returns 0.5
10.5 % 1; // returns 0.5
Number.isInteger(23); // true
Number.isInteger(1.5); // false
Number.isInteger("x"); // false:
Number.isInteger() is part of the ES6 standard and not supported in IE11.
It returns false for NaN
, Infinity
and non-numeric arguments while x % 1 != 0
returns true.
Number.isInteger(12.0)
returns true
.
number
is whole or not. If your input is a string, you need to convert it into a number
first e.g. via parseFloat()
, of course.
Number.isInteger(2.000000000000000000001)
// true
2.000000000000000000001 === 2
in JavaScript
Or you could just use this to find out if it is NOT a decimal:
string.indexOf(".") == -1;
yournumber.toString.indexOf(".")
Simple, but effective!
Math.floor(number) === number;
Math.floor(3.0) == 3.0
is true, Math.floor(3.3) == 3.3
is false
The most common solution is to strip the integer portion of the number and compare it to zero like so:
function Test()
{
var startVal = 123.456
alert( (startVal - Math.floor(startVal)) != 0 )
}
startVal != Math.floor(startVal)
?
//How about byte-ing it?
Number.prototype.isInt= function(){
return this== this>> 0;
}
I always feel kind of bad for bit operators in javascript-
they hardly get any exercise.
>>
converts the value to a signed 32-bit integer.
Number.isSafeInteger(value);
In JavaScript, isSafeInteger() is a Number method that is used to return a Boolean value indicating whether a value is a safe integer. This means that it is an integer value that can be exactly represented as an IEEE-754 double precision number without rounding.
Number.isInteger()
is probably the most concise. It returns true if it is an integer, and false if it isn't.
number = 20.5
if (number == Math.floor(number)) {
alert("Integer")
} else {
alert("Decimal")
}
Pretty cool and works for things like XX.0 too! It works because Math.floor() chops off any decimal if it has one so if the floor is different from the original number we know it is a decimal! And no string conversions :)
var re=/^-?[0-9]+$/;
var num=10;
re.test(num);
num= 999999999999999999999
.
function isDecimal(n){
if(n == "")
return false;
var strCheck = "0123456789";
var i;
for(i in n){
if(strCheck.indexOf(n[i]) == -1)
return false;
}
return true;
}
parseInt(num) === num
when passed a number, parseInt()
just returns the number as int:
parseInt(3.3) === 3.3 // false because 3 !== 3.3
parseInt(3) === 3 // true
parseInt(3.0) === 3.0 // true
convert number string to array, split by decimal point. Then, if the array has only one value, that means no decimal in string.
if(!number.split(".")[1]){
//do stuff
}
This way you can also know what the integer and decimal actually are. a more advanced example would be.
number_to_array = string.split(".");
inte = number_to_array[0];
dece = number_to_array[1];
if(!dece){
//do stuff
}
Use following if value is string (e.g. from <input
):
Math.floor(value).toString() !== value
I add .toString()
to floor to make it work also for cases when value == "1."
(ends with decimal separator or another string). Also Math.floor
always returns some value so .toString()
never fails.
Here's an excerpt from my guard library (inspired by Effective JavaScript by David Herman):
var guard = {
guard: function(x) {
if (!this.test(x)) {
throw new TypeError("expected " + this);
}
}
// ...
};
// ...
var number = Object.create(guard);
number.test = function(x) {
return typeof x === "number" || x instanceof Number;
};
number.toString = function() {
return "number";
};
var uint32 = Object.create(guard);
uint32.test = function(x) {
return typeof x === "number" && x === (x >>> 0);
};
uint32.toString = function() {
return "uint32";
};
var decimal = Object.create(guard);
decimal.test = function(x) {
return number.test(x) && !uint32.test(x);
};
decimal.toString = function() {
return "decimal";
};
uint32.guard(1234); // fine
uint32.guard(123.4); // TypeError: expected uint32
decimal.guard(1234); // TypeError: expected decimal
decimal.guard(123.4); // fine
You can multiply it by 10 and then do a "modulo" operation/divison with 10, and check if result of that two operations is zero. Result of that two operations will give you first digit after the decimal point. If result is equal to zero then the number is a whole number.
if ( (int)(number * 10.0) % 10 == 0 ){
// your code
}
function isDecimal(num) {
return (num !== parseInt(num, 10));
}
You can use the bitwise operations that do not change the value (^ 0
or ~~
) to discard the decimal part, which can be used for rounding. After rounding the number, it is compared to the original value:
function isDecimal(num) {
return (num ^ 0) !== num;
}
console.log( isDecimal(1) ); // false
console.log( isDecimal(1.5) ); // true
console.log( isDecimal(-0.5) ); // true
function isWholeNumber(num) {
return num === Math.round(num);
}
Perhaps this works for you?
It uses regex to check if there is a comma in the number, and if there is not, then it will add the comma and stripe.
var myNumber = '50';
function addCommaStripe(text){
if(/,/.test(text) == false){
return text += ',-';
} else {
return text;
}
}
myNumber = addCommaStripe(myNumber);
When using counters with decimal steps, checking if number is round will actually fail, as shown below. So it might be safest (although slow) to format the number with 9 (could be more) decimal places, and if it ends with 9 zeros, then it's a whole number.
const isRound = number => number.toFixed(9).endsWith('000000000'); for (let counter = 0; counter < 2; counter += 0.1) { console.log({ counter, modulo: counter % 1, formatted: counter.toFixed(9), isRound: isRound(counter) }); }
Function for check number is Decimal or whole number
function IsDecimalExist(p_decimalNumber) {
var l_boolIsExist = true;
if (p_decimalNumber % 1 == 0)
l_boolIsExist = false;
return l_boolIsExist;
}
Success story sharing
20.0
has a decimal point programmatically, unless it is expressed as a string. Also, none of the other solutions got a down vote for not tackling that ;-)"10."
is a whole number and the result will be exactly the same as"10"
or10
.