reportValidity polyfill for IE 10, 11

reportValidity.js

if (!HTMLFormElement.prototype.requestSubmit) {
    HTMLFormElement.prototype.requestSubmit = function() {
        const submitBtn = document.createElement('input');
        submitBtn.type = 'submit';
        submitBtn.hidden = true;
        this.appendChild(submitBtn);
        submitBtn.click();
        this.removeChild(submitBtn);
    };
}

if (!HTMLFormElement.prototype.reportValidity) {
    HTMLFormElement.prototype.reportValidity = function() {
        if (this.checkValidity()){
            return true;
        }
        if (this.noValidate){
            this.noValidate = false;
            this.requestSubmit();
            this.noValidate = true;
        } else {
            this.requestSubmit();
        }
        return false;
    };
}

Great work!
requestSubmit has a "submitter" argument
https://developer.mozilla.org/en-US/docs/Web/API/HTMLFormElement/requestSubmit
This can worn work (not tested):

if (!HTMLFormElement.prototype.requestSubmit) {
    HTMLFormElement.prototype.requestSubmit = function(submitter) {
        let submitBtn = submitter;
        if (!submitBtn) {
            submitBtn = document.createElement('input');
            submitBtn.type = 'submit';
            submitBtn.hidden = true;
            this.appendChild(submitBtn);
        }
        submitBtn.click();
        !submitter && this.removeChild(submitBtn);
    };
}