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How to display error without alert box using JavaScript ?
  • Last Updated : 02 Mar, 2020

Errors in JavaScript can be displayed without the use of alert boxes but using the alert box is the traditional way to do that. We can show errors with two methods without using the alert box.

Method 1: By using textContent property. The textContent is basically used to change the content of any node dynamically. With the help of this property we can display any content and draw user’s attention just like alert boxes

  • Syntax:
    node.textContent = "Some error message"
    
    // To draw attention
    node.style.color = "red";  
    
  • Example:
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    <!DOCTYPE html>
    <html lang="en">
      
    <head>
        <meta charset="UTF-8">
        <meta name="viewport" 
              content="width=device-width, 
                       initial-scale=1.0">
        <title>Demo</title>
        <style>
            h1 {
                color: green;
            }
            .container {
                padding: 15px;
                width: 400px;
            }
              
            label,
            input {
                margin-bottom: 10px;
            }
              
            button {
                float: right;
                margin-right: 10px;
                background-color: green;
            }
        </style>
    </head>
      
    <body>
        <center>
            <h1>GeeksforGeeks</h1>
            <b>Display error without alert box</b
            <br><br>
            <div class="container">
                <div>
                    <label>Uername:</label>
                    <input type="text" size="40">
                </div>
                <div>
                    <label>Phone no:</label>
                    <input type="text"
                           id="number" size="40">
                    <span id="error"></span>
                </div>
                <button type="submit" 
                        onclick="errorMessage()">
                    Submit
                </button>
            </div>
        </center>
    </body>
    <script>
        function errorMessage() {
            var error = document.getElementById("error")
            if (isNaN(document.getElementById("number").value)) 
            {
                  
                // Changing content and color of content
                error.textContent = "Please enter a valid number"
                error.style.color = "red"
            } else {
                error.textContent = ""
            }
        }
    </script>
      
    </html>

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  • Output:

Method 2: By using innerHTML property. The innerHTML can be used to changed selected node’s HTML. Instead of textContent and innerHTML, one can also use innerText which will lead to same output.

  • Syntax:
    node.innerHTML = "<span style='color: red;'>
                        Please enter a valid number
                      </span>"
  • Example:
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    <!DOCTYPE html>
    <html lang="en">
      
    <head>
        <meta charset="UTF-8">
        <meta name="viewport"
            content="width=device-width, 
                    initial-scale=1.0">
        <title>Demo</title>
        <style>
            h1 {
                color: green;
            }
            .container {
                padding: 15px;
                width: 400px;
            }
              
            label,
            input {
                margin-bottom: 10px;
            }
              
            button {
                float: right;
                margin-right: 10px;
                background-color: green;
            }
        </style>
    </head>
      
    <body>
        <center>
            <h1>GeeksforGeeks</h1>
            <b>Display error without alert box</b
            <br><br>
            <div class="container">
                <div>
                    <label>Uername:</label>
                    <input type="text" size="40">
                </div>
                <div>
                    <label>Phone no:</label>
                    <input type="text"
                        id="number" size="40">
                    <span id="error"></span>
                </div>
                <button type="submit"
                        onclick="errorMessage()">
                    Submit
                </button>
            </div>
        </center>
    </body>
    <script>
        function errorMessage() {
            var error = document.getElementById("error")
            if (isNaN(document.getElementById("number").value)) 
            {
      
                // Changing HTML to draw attention
                error.innerHTML = "<span style='color: red;'>"+
                            "Please enter a valid number</span>"
            } else {
                error.innerHTML = ""
            }
        }
    </script>
      
    </html>                    

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  • Output:

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