javaScript tutorial

javaScript tutorial

• 1.
  JavaScript Tutorial
• 2.
  HTML form validationcan be done by a JavaScript. • If a form field (fname) is empty, this function alerts a message, and returns false, to prevent the form from being submitted: • Example • function validateForm() { • var x = document.forms["myForm"]["fname"].value; • if (x == null || x == "") { • alert("Name must be filled out"); • return false; • } • }
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  This is theHTML that might goes with the Javascript in the previous slide. • <form name="myForm" action="demo_form.asp" onsubmit="return validateForm()" method="post"> Name: <input type="text" name="fname"> <input type="submit" value="Submit"> </form>
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  This is oneexample of what JavaScript can do to validate input from a user In this example if a user enters their name the JavaScript code will give the x variable that value. If the user does not enter their name an alert box opens telling the user that they must enter a name.
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  Data Validation Data validationis the process of ensuring that computer input is clean, correct, and useful. • Typical validation tasks are: • has the user filled in all required fields? • has the user entered a valid date? • has the user entered text in a numeric field?
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  • Most often,the purpose of data validation is to ensure correct input to a computer application. • Validation can be defined by many different methods, and deployed in many different ways. • Server side validation is performed by a web server, after input has been sent to the server. • Client side validation is performed by a web browser, before input is sent to a web server.