Can javascript simulate a button click?

A button may be always clicked programmatically. For example you may have a page with a form like this:

<form>    <input type="text" />    <button>Do something</button>    <input type="submit"></form>

then it is possible just to open debug console and type

document.getElementsByTagName('button')[0].click();

which will click the button, or

document.getElementsByTagName('input')[1].click();

which will click the submit button of the form, or just

document.forms[0].submit();

to submit the form without clicking the button.

There is no way to prevent user from mastering JavaScript code on client. You have to add some validation on server side in order to prevent unwanted user actions.

the only thing you can do is validate the request on the server.

once you hand the page over to a client, you have no technical control over how it might be used.

What you can do for example, from:

Say you're making javascript game. You use AJAX to send the score of the player tothe server for logging. After looking at the script, a malicious user could run your AJAX codeto send a score of 1,000,000 even if they earned only 5,000.

You can't prevent this from happening on the javascript side. However, there should some way to authenticate AJAX requests on the server side, you might be able to pass a security "token" to javascript that a hacker couldn't get ahold of.