How to trigger MathJax?

Question

I included MathJax with the script

<script type="text/javascript" async
  src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-MML-AM_CHTML">
</script>

This automatically replaces all math codes with the formatted tags.

1. How can I trigger MathJax by a javascript click only, instead of upon load.
2. How can I tell MathJax to put the formatted element at the end of the page instead of replacing the original code?

Answer 1

1. How can I trigger MathJax by a javascript click only, instead of upon load.

From docs: skipStartupTypeset: false

Normally MathJax will typeset the mathematics on the page as soon as the page is loaded. If you want to delay that process, in which case you will need to call MathJax.Hub.Typeset() yourself by hand, set this value to true.

---

Starting typeset

The MathJax.Hub.Typeset() command also accepts a parameter that is a DOM element whose content is to be typeset. That could be a paragraph, or a element, or even a MathJax math tag. It could also be the DOM id of such an object, in which case, MathJax will look up the DOM element for you. So

MathJax.Hub.Queue(["Typeset",MathJax.Hub,"MathExample"]);

would typeset the mathematics contained in the element whose id is MathExample. This is equivalent to

var math = document.getElementById("MathExample");
MathJax.Hub.Queue(["Typeset",MathJax.Hub,math]);

If no element or element id is provided, the whole document is typeset.

MathJax.Hub.Config({
    skipStartupTypeset: true,
    extensions: ["tex2jax.js", "TeX/AMSmath.js"],
    jax: ["input/TeX", "output/HTML-CSS"],
    tex2jax: {
        inlineMath: [["$", "$"]],
        processEscapes: true
    }
});

function startTypeSetting() {
  var HUB = MathJax.Hub;
  HUB.Queue(["Typeset", HUB, "render-me"]);
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-MML-AM_CHTML"></script>
<p id="render-me">$a+b=c$<p>

<button onClick="startTypeSetting()">Start typesetting</button>

2. How can I tell MathJax to put the formatted element at the end of the page instead of replacing the original code?

It would be better to know what are you trying to achieve, but here are 2 ways to skip typesetting for certain tags or classes, from tex2jax preprocessors configs:

MathJax.Hub.Config({
     tex2jax: {
         skipTags: ["script","noscript","style","textarea","pre","code"],
         ignoreClass: "tex2jax_ignore_1|tex2jax_ignore_2"
    }
}

You can copy the content of element you want to render to another element and start typesetting there:

MathJax.Hub.Config({
    skipStartupTypeset: true,
    extensions: ["tex2jax.js", "TeX/AMSmath.js"],
    jax: ["input/TeX", "output/HTML-CSS"],
    tex2jax: {
        inlineMath: [["$", "$"]],
        processEscapes: true
    }
});

function startTypeSetting() {
  //copy content from '#code-to-render' to '#render-point'
  var text = $('#code-to-render').val()
  $('#render-point').text(text)
  
  //Start typesetting
  var HUB = MathJax.Hub;
  HUB.Queue(["Typeset", HUB, "render-point"]);
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-MML-AM_CHTML"></script>

<textarea id="code-to-render">$a+b=c$</textarea>
<p id="render-point"></p>

<button onClick="startTypeSetting()">Start typesetting</button>