MathJax numbered equation equation ref tooltip

_mathjax-equation-numbering.gif

_README.md

MathJax numbered equation preview

No need to click on an a tag to see the equation, just hover on any <a> tag created using \eqref{label} and that's it!

Check https://mauriciopoppe.com/notes/mathematics/calculus/derivative/ for a live demo

Contents:

• index.html (the configuration I use for MathJax which enables equation numbers, see http://cdn.mathjax.org/mathjax/latest/test/sample-eqnum.html for more examples) (MathJaxV2)
• mathjaxPreview.js the scripts which enables the preview (MathJax V2)
• mathjaxPreviewV3.js the same script but with support for MathJax V3

index.html

<script type="text/javascript" src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML"></script>
<script type="text/x-mathjax-config">
  MathJax.Hub.Config({
    showProcessingMessages: false,
    messageStyle: 'none',
    tex2jax: {
      inlineMath: [['$','$']],
      displayMath: [['$$','$$']],
      processEnvironments: false
    },
    // show equation numbers
    TeX: {
      equationNumbers: {
        autoNumber: "AMS"
      }
    },
    'HTML-CSS': {
      imageFont: null
    }
  });
</script>

mathjaxPreview.css

.mathjax-tooltip {
  display: none;
  width: 100%;
  position: absolute;
}

mathjaxPreview.js

/*
 * MathJax eqn preview for a tags
 *
 * Copyright (c) 2015 Mauricio Poppe
 * Licensed under the MIT license.
 */
(function () {
  var $container = $(document.body);
  var $tooltip = $('<div />').addClass('mathjax-tooltip');
  $container.append($tooltip);

  function onMouseOver(ev) {
    var a = ev.currentTarget;
    var $number = $(a.hash);
    var $root = $number.closest('.MathJax_Display');
    var bounds = $(a).offset();
    var containerBounds = $container.offset();

    $tooltip.stop(true, true);
    $tooltip.append($root.clone());
    $tooltip.css({
      top: bounds.top - containerBounds.top - $tooltip.height() - 5,
      left: -1
    });
    $tooltip.fadeIn();
  }

  function onMouseOut(a) {
    $tooltip.stop(true, true);
    $tooltip.fadeOut(function () {
      $tooltip.empty();
    });
  }

  MathJax.Hub.Queue(function () {
    $container.on('mouseover', 'a[href*="mjx-eqn-"]', onMouseOver);
    $container.on('mouseout', 'a[href*="mjx-eqn-"]', onMouseOut);
  });

})();

mathjaxPreviewV3.js

/*
 * MathJax 3 equation preview, works with MathJax V3
 *
 * Copyright (c) 2020 Mauricio Poppe
 * Licensed under the MIT license.
 */
var container = document.body

var tooltip = document.createElement('div')
tooltip.classList.add('mathjax-tooltip')
Object.assign(tooltip.style, {
  display: 'none',
  width: '100%',
  position: 'absolute'
})
container.appendChild(tooltip)

function getTarget(ev) {
  return ev.currentTarget.closest('a')
}

function onMouseOver(ev) {
  var href = getTarget(ev)
  if (!href) return
  var number = document.querySelector(href.hash)
  var equation = number.closest('.MathJax')

  var equationBounds = equation.getBoundingClientRect()
  Object.assign(tooltip.style, {
    top: href.closest('.MathJax').offsetTop - equationBounds.height - 50 + 'px',
    display: 'block'
  })

  tooltip.appendChild(equation.cloneNode(true))
}

function onMouseOut(ev) {
  var href = getTarget(ev)
  if (!href) return
  tooltip.innerHTML = ''
  Object.assign(tooltip.style, { display: 'none' })
}

document.addEventListener('DOMContentLoaded', function () {
  ;(async function afterMathJaxRender() {
    await MathJax.startup.promise
    Array.from(document.querySelectorAll('.MathJax_ref')).forEach((el) => {
      el.addEventListener('mouseover', onMouseOver)
      el.addEventListener('mouseout', onMouseOut)
    })
  })()
})

I updated this script to work with MathJax v3, see the mathjaxPreviewV3.js file and the demo here: https://www.mauriciopoppe.com/notes/mathematics/calculus/derivative/

I am still confused about where exactly to use the preview script, I keep running into this error "Uncaught TypeError: Cannot read property 'appendChild' of null" Are you having the javascript render html for the tooltip?

After working a little bit further I am running into this error in the script Cannot read property 'closest' of null.

var equation = number.closest('.MathJax') - this line seems to be the source of the error but I am not sure how to fix it

var equation = number.closest('.MathJax') - this line seems to be the source of the error but I am not sure how to fix it

For MathJax v3, the container is mjx-container (not .MathJax); I also changed href.hash to href.getAttribute('href') (and switched to bottom positioning with reversed subtraction of bounding box values).

In the specific example on the website, he is somehow able to get the equation to display in the foreground. That is not happening for us. You still see the text behind the popup. Is there something else that he is also doing? Also, the equation only pops up if we hover over a specific part of the number and flickers. Is there a way around this @pkra @mauriciopoppe

In the specific example on the website, he is somehow able to get the equation to display in the foreground. That is not happening for us. You still see the text behind the popup. Is there something else that he is also doing?

That looks like CSS interference -- hard to tell without a live sample.

Also, the equation only pops up if we hover over a specific part of the number and flickers.

You could add the listeners to el.closest('mjx-container') instead (and then modify getTarget to return ev.currentTarget.querySelector('a') to drill down to the link again).

The flickering was a styling issue, I fixed it by moving the cloned formula a little bit above the link with

  Object.assign(tooltip.style, {
    top: href.closest('.MathJax').offsetTop - equationBounds.height - 50 + 'px',
    display: 'block'
  })

For positioning it depends where your cloned element is with respect to the original one, if it's a sibling and the cloned element comes after the original then it'll be on top without any z-style fixes, I used var container = document.body as the container element but it could be a sibling too.

I am not exactly sure what you mean by a little bit above the link. I have the exact same formula and it is still flickering.

Should I just change the container to be a sibling then?