JavaScript Number isInteger() Method

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The JavaScript Number isInteger() method is a static method used to determine whether the passed value is an integer or not. It returns a boolean value 'true' if the passed value is an integer. Otherwise, it returns 'false'.

In mathematics, integers are whole numbers that can be positive, negative, or zero, such as {1, 2, 3, 4, ..., 0, -1, -2, -3, ...}.

Syntax

Following is the syntax of JavaScript Number isInteger() method −

Number.isInteger(value)

Parameters

This method accepts a parameter named 'value', which is described below −

  • value − The value to be checked for an integer.

Return value

This method returns 'true' if the passed value is an integer; 'false' otherwise.

Example 1

If we pass a positive value to this method, it will return 'true'.

In the program below, we use the isInteger() method to determine whether the passed value '10' is an integer or not.

<html>
<head>
<title>JavaScript isInteger() Method</title>
</head>
<body>
<script>
   let num = 10;
   document.write("Is number ", num, " is an Integer? ", Number.isInteger(num));
</script>
</body>
</html>

Output

The program mentioned above returns a boolean value 'true' for the value 10 as −

Is number 10 is an Integer? true

Example 2

If we pass null as an argument to this method, it returns 'false'.

Following is another example of the isInteger() method. We pass 'null' as an argument to this method to check whether it is an integer or not.

<html>
<head>
<title>JavaScript isInteger() Method</title>
</head>
<body>
<script>
   let val = null;
   document.write("Is '", val, "' is an Integer? ", Number.isInteger(val));
</script>
</body>
</html>

Output

Once the above program is executed, it will return 'false' in the output as −

Is 'null' is an Integer? false

Example 3

Let's pass 0 (zero) as an argument to the 'isInteger()' method to verify whether it is an integer or not.

<html>
<head>
<title>JavaScript isInteger() Method</title>
</head>
<body>
<script>
   let val = 0;
   document.write("Is '", val, "' is an Integer? ", Number.isInteger(val));
</script>
</body>
</html>

Output

The above program returns 'true' for value 0 as −

Is '0' is an Integer? true

Example 4

The following example demonstrates the usage of the isInteger() method.

<html>
<head>
<title>JavaScript isInteger() Method</title>
</head>
<body>
<script>
   document.write("Is the result of 15/0 is an Inetger? ", Number.isInteger(10/0));
</script>
</body>
</html>

Output

The result of ( 15/0 ) is 'infinity', so the above program returns 'false' for the result of this value −

Is the result of 15/0 is an Inetger? false

Example 5

The example shown below will demonstrate the real-time usage of the JavaScript Number isInteger() method.

<html>
<head>
<title>JavaScript isInteger() Method</title>
</head>
<body>
<script>
   //declaring function
   function print(x, y){
      if(Number.isInteger(x/y)){
         document.write("Ok")
      }
      else{
         document.write("Not ok");
      }
   }
   let x = 10;
   let y = 5;
   document.write("x = ", x);
   document.write("<br> y = ", y);
   //call the function
   document.write("<br>Result1 = ")
   print(x, y);
   //output will be 'Ok', 

   let n1 = 14.5
   let n2 = 5;
   document.write("<br> n1 = ", n1);
   document.write("<br> n2 = ", n2);
   //call the function
   document.write("<br>Result2 = ")
   print(n1, n2);
   //output will be 'Not ok', because decimal number can't be consider as an integer value
</script>
</body>
</html>

Output

The program displays the statements 'Ok' and 'Not ok' based on the specified condition −

x = 10
y = 5
Result1 = Ok
n1 = 14.5
n2 = 5
Result2 = Not ok
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