Create embedded hover-Footnotes for Ghost 1.0's default theme

embedded-hover-footnotes.html

<!-- Thanks to w3schools for the base sample implementation:
      https://www.w3schools.com/howto/howto_css_tooltip.asp
      
      Put this in the "Code inject" of your Ghost 1.0 Blog Footer. -->
<style>
.tooltip {
    position: relative;
}

.tooltip .tooltiptext {
    visibility: hidden;
    width: 240px;
    background-color: #555;
    color: #fff;
    text-align: center;
    border-radius: 6px;
    padding: 5px 0;
    position: absolute;
    z-index: 1;
    bottom: 90%;
    left: 50%;
    margin-left: -120px;
    opacity: 0;
    transition: opacity .5s;
    line-height: 1.1em;
    font-size: 90%;
    padding: .5em;
}

.tooltip .tooltiptext * {
    color: #fff;
}
    
.tooltip .tooltiptext::after {
    content: "";
    position: absolute;
    top: 100%;
    left: 50%;
    margin-left: -5px;
    border-width: 5px;
    border-style: solid;
    border-color: #555 transparent transparent transparent;
}

.tooltip:hover .tooltiptext {
    visibility: visible;
    opacity: 1;
}
    
.tooltip a.footnote-backref {
    display: none;
}
</style>
<script>
    var createTooltip = function(tooltiptext) {
        var tooltip = document.createElement('span');
        tooltip.setAttribute('class', 'tooltiptext');
        tooltip.innerHTML = tooltiptext;
        return tooltip;
    }
    var appendTooltipTo = function(element, tooltipText) {
        element.append(createTooltip(tooltipText));
    }
    var processTooltip = function(footnoteid) {
        var footnotep = document.getElementById(footnoteid).querySelector('p');
        var footnotetext = footnotep.innerHTML;
        var footnoterefid = document.getElementById(footnoteid).querySelector('a.footnote-backref').getAttribute('href').substring(1);
        var footnoteref = document.getElementById(footnoterefid);
        footnoteref.setAttribute('class', 'tooltip');
        appendTooltipTo(footnoteref, footnotetext);
    }
    var footnotes = document.querySelectorAll('li.footnote-item');
    [].forEach.call(footnotes, function( element ) {
  		processTooltip(element.getAttribute('id'));
	});
</script>