How to change the color of a button when the input field is filled – JavaScript?

Javascript Web Development Front End Technology Object Oriented Programming

Let’s say the following is our button −

<button id="buttonDemo" style="background:skyblue;margin-left:10px;">Press Me</button>

On filling the below input field, the color of the above button should change −

<input type="text" id="changeColorDemo" style="margin-left:10px;margin-top:10px" onkeyup="changeTheColorOfButtonDemo()">

Example

Following is the code −

Live Demo

<!DOCTYPE html>
<html lang="en">
<head>
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
   <title>Document</title>
</head>
<link rel="stylesheet" href="//code.jquery.com/ui/1.12.1/themes/base/jquery-ui.css">
<script src="https://code.jquery.com/jquery-1.12.4.js"></script>
<script src="https://code.jquery.com/ui/1.12.1/jquery-ui.js"></script>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css" rel="stylesheet" />
<body>
   <label>
      UserName:
   </label>
   <input type="text" id="changeColorDemo" style="margin-left:10px;margin-top:10px"
      onkeyup="changeTheColorOfButtonDemo()">
   <br><br>
   <button id="buttonDemo" style="background:skyblue;margin-left:10px;">Press Me</button>
</body>
<script>
   function changeTheColorOfButtonDemo() {
      if (document.getElementById("changeColorDemo").value !== "") {
         document.getElementById("buttonDemo").style.background = "green";
      } else {
         document.getElementById("buttonDemo").style.background = "skyblue";
      }
   }
</script>
</html>

To run the above program, save the file name “anyName.html(index.html)”. Righ click on the file and select the option “Open with Live Server” in Visual Studio Code editor.