使用确认功能.就像警报一样工作，但是如果用户按确定"，则返回true，如果按取消"，则返回false.

Use the confirm function. Works just like an alert, but returns true if user presses okay, false if they press cancel.

test = confirm("Continue?");

if (test) {
    this.form.submit()
}

因此，对于您来说，您可以将其作为on

so for you, you'd put it on your onchange as

onchange="if(confirm('Continue?')){this.form.submit()}"