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The following sequence diagrams show this approach in action. The form submitted by the user will be validated by the server-side PHP script named login. If the validation check passes, the server will log in the user, otherwise the server will return the errors to the user for correction. Thanks to JS and Ajax, this user experience can be improved a lot.
A better solution is to perform a client-side validation using JS, which bring us to the second sequence diagram. If the client-side i. But if the client-side validation does not pass, we do not need to make a round-trip to the server and we can immediately return the errors to the user.
But we still have some problems. The client-side validation cannot check if the username is registered. This bring us to Ajax and the third sequence diagram. The user experience has now been much more enhanced. The Ajax call communicates with the server e. In this tutorial, we are going to limit ourselves to the client-side validation scenario without implementing the server-side validation or the Ajax call to the server. We will implement those in subsequent, more advanced tutorials.
The JS validateForm function gets email and password ids from form input and verifies that both have a value. The validateForm function returns true if the validation passes, false otherwise. Now let's write some CLJS code. Create the file login. As you can see, this ported code defines two functions: validate-form and init.
I dove deeper in Node. In the past, you would need other languages to develop great mobile applications, like Objective-C for iOS or Java for Android. This means that you can use mobile devices features, such as the camera or localization to build JS-powered apps.
Front-end Developer Handbook 12222
For developers, JS is easy to learn and fast to get into active development.
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