Javascript validation error message display
In this tutorial you will learn how to validate an HTML form using JavaScript. Show
Understanding Client-Side ValidationWeb forms have become an essential part of web applications. It is often used to collect user's information such as name, email address, location, age, and so on. But it is quite possible that some user might not enter the data what you've expected. So to save bandwidth and avoid unnecessary strain on your server resources you can validate the form data on client-side (i.e. user's system) using JavaScript before passing it onto the web server for further processing. Client-side validation is also helpful in creating better user experience, since it is faster because validation occurs within the user's web browser, whereas server-side validation occurs on the server, which require user's input to be first submitted and sent to the server before validation occurs, also user has to wait for server response to know what exactly went wrong. In the following section we will take a closer look at how to perform JavaScript form validation and handle any input errors found appropriately and gracefully. Note: Client-side validation is not a substitute or alternative for server-side validation. You should always validate form data on the server-side even if they are already validated on the client-side, because user can disable JavaScript in their browser. Form Validation with JavaScriptThe form validation process typically consists of two parts— the required fields validation which is performed to make sure that all the mandatory fields are filled in, and the data format validation which is performed to ensure that the type and format of the data entered in the form is valid. Well, let's get straight to it and see how this actually works. Creating the HTML FormLet's first create a simple HTML form that we will validate on client-side using JavaScript when the user clicks on the submit button. Well, let's create an HTML file named "application-form.html" and place the following code in it, then save it somewhere on your system.
Building the Form Validation ScriptNow we're going to create a JavaScript file that holds our complete validation script. Well, let's create a JavaScript file named "validator.js" and place the following code inside it, then save it at the same location where you've saved the previous HTML file. Go through each line of the following example code to understand how JavaScript validation works:
The value of an individual form field can be accessed and retrieved using the syntax Also, to check whether the format of input data is correct or not we've used the regular expressions. It is one of the most effective techniques for validating the user inputs. Furthermore, the above script will also display the data entered by the user in an alert dialog box for preview purpose before submitting the form to the web server. Tip: However, you can validate email format using regular expression. But a user might enter an email that is correctly formatted but does not exist. So for authentic email validation, send confirmation email to the user and verify whether the email really exists or not. Adding Style Sheet to Beautify the FormFinally, create the file named "style.css" and place the following code in it, then save it also at the same location where you've saved the previous two files. These are the style rules to beautify our form.
That's all, now open the "application-form.html" file in a web browser and try to fill some data and see how the script respond when an invalid data is entered in a form field. To learn about server-side validation, please check out the tutorial on PHP form validation How do you display error messages in JavaScript?The common ways to show error messages in Javascript are:. Error messages will show in the developer's console by default. In major browsers, press F12 to show the console. ... . Use try { CODE } catch (e) { alert(e); } to show the error message a dialog box.. Lastly, create custom error notifications in HTML.. How do you show validation error in HTML?You can now use the HTMLFormElement. reportValidity() method, at the moment it's implemented in most browsers except Internet Explorer (see Browser compatibility at MDN). It reports validity errors without triggering the submit event and they are shown in the same way.
How do I show error below input field?To customize the appearance and text of these messages, you must use JavaScript; there is no way to do it using just HTML and CSS. HTML5 provides the constraint validation API to check and customize the state of a form element. var email = document. getElementById("mail"); email.
How do I display an error beside a textbox in HTML?Add an ID and access your input field. And change your html field like this.. Use of NULL: it is null and not NULL.. No id assigned as firstname and checking for that in the if loop.. to give value to span need to use innerHTML.. |