Trigger standard HTML5 validation (form) without using submit button?

You can use reportValidity, however it has poor browser support yet. It works on Chrome, Opera and Firefox but not on IE nor Edge or Safari:

var myform = $("#my-form")[0];
if (!myform.checkValidity()) {
    if (myform.reportValidity) {
        myform.reportValidity();
    } else {
        //warn IE users somehow
    }
}

(checkValidity has better support, but does not work on IE<10 neither.)