How to Check if Variable is String in Javascript

18 Jun 2022

You use the typeof operator in Javascript to check if a variable is a string. The typeof operator returns a value of string when the variable is a string.

Javascript string variable Check poster

Simple String Check Example in Javascript

var computerbrands = ["Apple","HP","Dell","Lenovo","Acer","Asus"];
var slogantext = "Road rage burns the tires.";
typeof(computercompanies);
// object
typeof(slogantext);
// string

Using Conditionals

In most instances you will check if a variable an array with an if statement.

var slogantext = "Road rage burns the tires.";
if(typeof(slogantext)=== 'string'){
  // Do something if the variable is a string
} else {
  // Do something else if the variable is not a string
}

Using a Function

var slogantext = "Road rage burns the tires.";
var computerbrands = ["Apple","HP","Dell","Lenovo","Acer","Asus"];
function checkIfString(variable){
  if(typeof(variable)=== 'string'){
    return true;
  } else {
    return false;
  }  
}
checkIfString(slogantext);
// true
checkIfString(computerbrands);
// false

Displaying Results on a Webpage

Code

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width">
    <title>Check If Variable is String</title>
  </head>
<body>
  <h1 id="slogan">Waiting for Slogan...</h1>
  <script>
    var slogantext = "Road rage burns the tires";
    var computerbrands = ["Apple","HP","Dell","Lenovo","Acer","Asus"];
    var slogan = document.getElementById('slogan');
    function checkIfString(variable){
      if(typeof(variable)=== 'string'){
        slogan.innerHTML(slogantext);
      } else {
         slogan.innerHTML("No Slogan");
      }  
    }
    checkIfString(computerbrands);
    checkIfString(slogantext);
  </script>
</body>

</html>

Results

Screenshot of Checking String Variable

You can interact with the complete code on: https://check-string-js.avicndugu.repl.co.