reportValidity polyfill for IE 10, 11

reportValidity.js

/**
Only work if your form has a submit button
*/
if ( ! HTMLFormElement.prototype.reportValidity) {
  
  HTMLFormElement.prototype.reportValidity = function () {
    
    var validity = this.checkValidity();
    
    if ( ! validity) {
      var submitButtons = this.querySelectorAll("button, input[type=submit]");

      for (var i = 0; i < submitButtons.length; i++) {
        if (submitButtons[i].type === "submit") {
          submitButtons[i].click();
          return validity;
        }
      }
    }

    return validity;
  }
}

another shot - doesn't matter if a form has multiple submit buttons, does matter if a form has a nosubmit attribute
https://gist.github.com/mcshaz/c65040c11e6daffe356cbedb7ec84ce4

Thanks, worked for me!