# Using mathjax in an updating sequence in javascript

I have four dynamic variables in my program,

xzero, xone, xtwo, xthree


That represent the coefficients of a cubic function. I want to show the actual equation in the HTML, in the following format:

xthree*x^3+xtwo*x^2+xone*x+xzero=f(x)


but it needs to be able to update with the variables, so I had originally thought that I would do a

document.getElementById("demo").innerHTML = (new equation);


But it seems to me that either mathJax doesn't work in javascript, or that I'm not doing it right. The only alternative solution that I could think of is to make four individual div tags per variable, and update them all, but this seems unnecessarily clunky. Could I get some pointers either way as to how I would fix this?

## Answers:

MathJax automagically renders the document when it is loaded, but not later. Try explicitly requesting re-render:

document.getElementById("demo").innerHTML = "...";
MathJax.Hub.Queue(["Typeset", MathJax.Hub, 'demo']);


EDIT: After some thinking, I figured you could ask for the render in one element, keep it hidden, then copy the finished markup into another, to prevent flicker:

var mathDiv = document.getElementById('math');
var displayDiv = document.getElementById('display');

MathJax.Hub.Queue(["Typeset",MathJax.Hub,"math"]);
MathJax.Hub.Queue(function() {
var math = MathJax.Hub.getAllJax("MathDiv")[0];
var i = 1;
setInterval(function() {
MathJax.Hub.Queue(["Text", math, "\\int_0^{" + i + "} x dx"]);
MathJax.Hub.Queue(function() {
displayDiv.innerHTML = mathDiv.innerHTML;
});
i++;
}, 1000);
});
#math {
display: none
}
<script type="text/javascript"
src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.0/MathJax.js?config=TeX-AMS-MML_HTMLorMML">
</script>
<div id="math"></div>
<div id="display"></div>

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