How to Check if Variable is String or Integer in Javascript
In this tutorial, you will learn how to check if variable is string or integer in javascript. A variable that holds a plain text as its value is considered to be of string type. There are certain primitive types in javascript and number is one of them. As the name suggests, any variable that holds a number as its value is considered to be of number type.
There is no dedicated data type that represents integer in javascript. All the numbers or numeric values are of number type. Since we have integer type in various other programming languages, we mistakenly refer numeric values as integer type in javascript. The point to be noted here is that only a round number or whole number is considered to be a valid integer.
There are numerous ways to check if a variable is string or integer. We are going to use one of the easiest solutions which involve the usage of the typeof
and ternary (?
) operators. The typeof
operator returns the type of the variable. The ternary operator is also known as the conditional operator which acts similar to the if-else statement.
In the following example, we have one global variable and upon click of a button, we will check if the variable is string or integer and display the result on the screen. Please have a look over the code example and the steps given below.
HTML & CSS
- We have 3 elements in the HTML file (
div
,button
, andh1
). Thediv
element is just a wrapper for the rest of the elements. - The
innerText
for thebutton
element is“Check”
and for theh1
element, it is“Result”
. - We have done some basic styling using CSS and added the link to our
style.css
stylesheet inside thehead
element. - We have also included our javascript file
script.js
with ascript
tag at the bottom.
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <link rel="stylesheet" href="style.css"> <title>Document</title> </head> <body> <div> <button>Check</button> <h1>Result</h1> </div> <script src="script.js"></script> </body> </html>
body { text-align: center; } div { display: inline-block; } button { display: inline-block; padding: 10px 20px; }
Javascript
- We have selected the
button
element andh1
element using thedocument.querySelector()
method and stored them inbtnCheck
andresult
variables respectively. - We have a global variable
myVar
which holds a string as its value. - We have attached a
click
event listener to thebutton
element. - In the event handler function, we are calling
checkVariable()
method and passing itmyVar
as a parameter. This method will verify whethermyVar
is string or integer. - In the
checkVariable()
method, we are usingtypeof
and ternary (?
) operators as well asswitch
statement for verification. Depending upon the result of the check, this method will return“Integer”
,"String"
or“Not String or Integer”
. - We are displaying the returned value in the
h1
element using theinnerText
property.
let btnCheck = document.querySelector("button"); let output = document.querySelector("h1"); let myVar = 'Hello World'; btnCheck.addEventListener("click", () => { output.innerText = verify(myVar); }); function verify(val) { let result = Number.isInteger(val) ? 1 : 0; if (result == 0) result = typeof val == "string" ? 2 : result; switch (result) { case 1: return "Integer"; case 2: return "String"; default: return "Not String or Integer"; } }