How to check if a number evaluates to Infinity using JavaScript ?

Last Updated : 18 Oct, 2019

The task is to check whether number evaluates to infinity or not with the help of JavaScript. Here are few techniques discussed.
Approach 1:

Checking if number is equal to Number.POSITIVE_INFINITY or Number.NEGATIVE_INFINITY .

Example 1: This example uses the approach as discussed above.

<!DOCTYPE HTML> 
<html> 
  
<head> 
    <title> 
        Check if a Number evaluates to Infinity. 
    </title> 
</head> 
  
<body style="text-align:center;"
      id="body"> 
    <h1 style="color:green;" 
        id="h1">   
            GeeksForGeeks   
        </h1> 
    <p id="GFG_UP"
       style="font-size: 15px;  
              font-weight: bold;"> 
    </p> 
    <button onclick="GFG_Fun()"> 
        click here 
    </button> 
    <p id="GFG_DOWN" 
       style="color:green;  
              font-size: 20px;  
              font-weight: bold;"> 
    </p> 
    <script> 
        var up = document.getElementById('GFG_UP'); 
        var down = document.getElementById('GFG_DOWN'); 
        var n = 1 / 0; 
        up.innerHTML = "Click on the button to check if"+ 
          " Number evaluates to Infinity.<br> Number = 1/0"; 
  
        function GFG_Fun() { 
            if (n == Number.POSITIVE_INFINITY || n == Number.NEGATIVE_INFINITY) { 
                down.innerHTML = "Infinity"; 
            } else { 
                down.innerHTML = "Not Infinity"; 
            } 
        } 
    </script> 
</body> 
  
</html> 

Output:

Before clicking on the button:
After clicking on the button:

Approach 2:

Using Number.isFinite() method to check if the number is finite or not.

Example 2: This example uses the approach as discussed above.

<!DOCTYPE HTML> 
<html> 
  
<head> 
    <title> 
        Check if a Number evaluates to Infinity. 
    </title> 
</head> 
  
<body style="text-align:center;"> 
    <h1 style="color:green;">   
            GeeksForGeeks   
        </h1> 
    <p id="GFG_UP" 
       style="font-size: 15px; 
              font-weight: bold;"> 
    </p> 
    <button onclick="GFG_Fun()"> 
        click here 
    </button> 
    <p id="GFG_DOWN" 
       style="color:green;  
              font-size: 20px;  
              font-weight: bold;"> 
    </p> 
    <script> 
        var up = document.getElementById('GFG_UP'); 
        var down = document.getElementById('GFG_DOWN'); 
        var n = 1 / 4; 
        up.innerHTML = "Click on the button to check if"+ 
          " Number evaluates to Infinity.<br> Number = 1/4"; 
  
        function GFG_Fun() { 
            if (!Number.isFinite(n)) { 
                down.innerHTML = "Infinity"; 
            } else { 
                down.innerHTML = "Not Infinity"; 
            } 
        } 
    </script> 
</body> 
  
</html> 

Output:

Before clicking on the button:
After clicking on the button:

My Personal Notes

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