Validating html forms with javascript

To find out which value (if any) has been selected, you need to loop through the array until you find which one has been selected: In the case of a single radio button we have nothing to loop through so just return either it's value, if the radio button is checked, or false.

If you're working with arrays of checkboxes to submit data to a server-side script then you might already have some grey hairs from trying to figure out how to validate the input using Java Script.

The problem is that, to have the data submitted in a 'nice' format to the server, the function returns an array containing all the selected checkbox values. In more complicated forms you will want to set conditions on the form that combine multiple elements.

Normally you would modify this so that you could submit or not submit the form based on the number of items selected. For example, a text input that only needs to have a value if a checkbox is checked: Using simple logical operators and the functions supplied above you can do all sorts of client-side form validation.

Validating form input with Java Script is easy to do and can save a lot of unnecessary calls to the server as all processing is handled by the web browser.It explains some of the code examples above as well as introducing more advanced concepts: Very new to coding. Would be great if you could post full examples of code including form and not just pieces that fit into the greater framework of code.I've coded a working form, all checks are great but for some reason the hardest part is trying to stop form submission before validation.When form input is important, it should always be verified using a secure server-side script.Otherwise a browser with Java Script disabled, or a hacker trying to compromise your site, can easily submit invalid data. The first test in the example is therefore only necessary in order to provide a different error message when the input is blank.

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