This repl parses lots of mathy expressions including LaTeX, Python, JS, and regular math.
To view this on TripleLog, click here.
The HTML is a simple input/output to change a string of text. Each step is output including each step of the postfixing.
Add CSS by editing the style.css file that is linked to in the head section or inline edit the style section in the head.
The prec.js file just creates the precendence map. The clean.js file makes some adjustments to the input to be easier to postfix and parses some LaTeX like matrices, derivatives, and more. The postfix.js file then postfixes the cleaned string. There is also some JavaScript in the index.html that puts it all together.