I have one HTML
It is more appropriate to approach this problem with the mentality that a form will have a default action tied to one submit button, and then an alternative action bound to a plain button. The difference here is that whichever one goes under the submit will be the one used when a user submits the form by pressing enter, while the other one will only be fired when a user explicitly clicks on the button.
Anyhow, with that in mind, this should do it:
With this javascript:
var form = document.getElementById('myform');
form.onsubmit = function() {
form.target = '_self';
};
document.getElementById('btn2').onclick = function() {
form.target = '_blank';
form.submit();
}
Approaches that bind code to the submit button's click event will not work on IE.