Use TeX in alt-text of images for rendering with MathJax

img-to-mj.js

(function () {
var images = document.getElementsByTagName('img');
var hasMath = false;
for (var i = 0; i < images.length; i++){
  var image = images[i];
  tex = image.getAttribute('alt');
  if (tex && tex[0] === '$'){ // TODO a class for TeX images would be cleaner, also to differentiate inline and display math
    hasMath = true;
    var preview = document.createElement('span');
    preview.setAttribute('class','MathJax_Preview');
    image.parentNode.insertBefore(preview, image);
    preview.appendChild(image);
    var script = document.createElement('script');
    script.type = 'math/tex';
    script.text= tex.substring(1,tex.length-1); // strip dollars from TeX string
    preview.parentNode.insertBefore(script, preview.nextSibling)
  }
}
if (hasMath){ //if there's math, load MathJax
  var mathjax = document.createElement('script');
  mathjax.src= 'https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS_CHTML-full';
  document.head.appendChild(mathjax);
}
})();