How To Determine Which Submit Button Was Pressed, Form onSubmit Event, Without jQuery [duplicate]

<form onsubmit="alert(this.submitted); return false;">
    <input onclick="this.form.submitted=this.value;" type="submit" value="Yes" />
    <input onclick="this.form.submitted=this.value;" type="submit" value="No" />
</form>

jsfiddle for the same