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

Last Updated : 09 Dec, 2022

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

Approach 1: Checking if the number is equal to the Number.POSITIVE_INFINITY or Number.NEGATIVE_INFINITY .

Example: This example uses the approach discussed above.

html

<body style="text-align:center;"> 
      id="body"> 
    <h1 style="color:green;" 
        id="h1"> 
        GeeksForGeeks 
    </h1> 
    <h3> 
        Check if number is Infinity? 
    </h3> 
    <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> 

Output:

Approach 2: Using Number.isFinite() method to check if the number is finite or not.

Example: This example uses the approach discussed above.

html

<body style="text-align:center;"> 
    <h1 style="color:green;"> 
        GeeksForGeeks 
    </h1> 
    <h3> 
        Check if number is Infinity? 
    </h3> 
    <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> 