To check if a variable is not a number in javascript; Through this tutorial, i am going to show you how to check whether a variable or given value is number or not in javascript.
Check if variable is a number in JavaScript
In JavaScript, there are two ways to check if a variable is a number :
- isNaN() JavaScript – isNaN Stands for “is Not a Number”, if a variable or given value is not a number, it returns true, otherwise it will return false.
- typeof JavaScript – If a variable or given value is a number, it will return a string named “number”. In JavaScript, the typeof operator returns the data type of its operand in the form of a string.
1. isNaN JavaScript
Using the JavaScript’s “isNaN
” method, you can check if a variable is a number in javascript; as follows:
<!DOCTYPE html> <html> <title>Check if variable is a number or not in JavaScript Using isNaN()</title> <head></head> <body> <h1>Check if variable is a number or not in JavaScript Using isNaN()</h1> <input type="text" id="demo" value="" placeholder="Please enter here....."> <button onclick="myFunction()">Click & See Result</button> <script type="text/javascript"> function myFunction() { var num = document.getElementById("demo").value; console.log(num); if(isNaN(num)){ alert(num + " is not a number"); }else{ alert(num + " is a number"); } } </script> </body> </html>
2. typeof JavaScript
Using the JavaScript’s “typeof
” operator, you can check if a variable is a number in javascript; as follows:
<!DOCTYPE html> <html> <title>Check if variable or given value is a number or not in JavaScript Using javascript Typeof</title> <head></head> <body> <h1>Check if variable or given value is a number or not in JavaScript Using javascript Typeof</h1> <input type="text" id="demo1" value="" placeholder="Please enter here....."> <button onclick="javascriptTypeof()">Click & See Result</button> <script type="text/javascript"> function javascriptTypeof() { var num = document.getElementById("demo1").value; if(typeof num == 'number'){ alert(num + " is a number"); }else{ alert(num + " is not a number"); } } </script> </body> </html>
Conclusion
To check if a variable is not a number in javascript; In this tutorial, you have learned easy two ways to check a given value is number or not with example and live demos.
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