Javascript Can Not Prevent Submit On Jsp Page, Why?

I have simple form and I want to submit button, but with confirmation, but in two cases form do submit, I cant stop submit even if I click cancel after confirm window appear her is

Solution 1:

You need to return the return value from your function where you call it:

<button type="submit" id="SaveIt"  onclick="return submitPost(this);" name="finalise" value="setme">TEST ME</button>
                                            ^^^^^^ here