How to Check if String Contains Decimal in Javascript

In this tutorial, you will learn how to check if string contains decimal in javascript. In a standard keyboard layout, the dot (.) key is located right before the forward slash key. A dot is also called decimal when it is used with numbers to separate fractional part from the whole number part.

There are numerous ways to check if a string contains a decimal. But for the sake of simplicity, we will use the includes() method and ternary operator (?) to accomplish our goal. The includes() method is used to perform a case-sensitive search to detect whether a string contains another string or not and returns a Boolean value.

In the following example, we have one global variable that holds a string. Upon click of a button, we will check if the string contains a decimal 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, and h1). The div element is just a wrapper for the rest of the elements.
  • The innerText for the button element is “Check” and for the h1 element, it is “Result”.
  • We have done some basic styling using CSS and added the link to our style.css stylesheet inside the head element.
  • We have also included our javascript file script.js with a script 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 class="container">    
    <button>Check</button>
    <h1>Result</h1>
  </div>

  <script src="script.js"></script>
</body>

</html>
.container {        
    text-align: center;
}

button {
  margin-top: 10px;
  padding: 10px 20px;
}

Javascript

  • We have selected the button element and h1 element using the document.querySelector() method and stored them in btnCheck and output variables respectively.
  • We have attached a click event listener to the button element.
  • We have a global variable myString which holds a string as its value.
  • In the event handler function, we are using the includes() method and ternary operator (?) to verify whether myString contains a decimal or not. Depending upon the result of the check, we will assign “Yes” or “No” to the result variable.
  • We are displaying the result in the h1 element using the innerText property.
let btnCheck = document.querySelector("button");
let output = document.querySelector("h1");

let myString = "This string contains dot.";

btnCheck.addEventListener("click", () => {

  let result = myString.includes(".") ? "Yes" : "No";
  output.innerText = result;
  
});