Highlight part of a math expression

Question

The following compiles under LaTeX

\(\left.x\right|_{x\gets\colorbox{yellow}{\(\mathsmaller{+2+h}\)}}\)

but how do I modify it to render under MathJaX?

Note: \colorbox is listed at http://docs.mathjax.org/en/latest/tex.html#tex-commands

but not at http://www.onemathematicalcat.org/MathJaxDocumentation/TeXSyntax.htm#C

P.S. I hope this is the right place to ask. If not, where?

Answer 1

That does not compile under LaTeX. This compiles under LaTeX:

\documentclass{article}
\usepackage{amsmath,color,relsize}
\begin{document}
\(\left.x\right|_{x\gets\colorbox{yellow}{\(\mathsmaller{+2+h}\)}}\)
\end{document}

The relevant point is that the commands \colorbox and \mathsmaller come from the packages color and relsize, respectively.

The \colorbox command is supported by MathJax because the color package has been implemented for MathJax, but you must use \require{color}, which is MathJax's method of loading a package.

The relsize package has not (currently) been implemented for MathJax, so that even writing \require{relsize} will not help, there is no way to use the \mathsmaller command.

The best you can do is something like

$$ \require{color} \left.x\right|_{x\gets\colorbox{yellow}{$+2+h$}} $$

which produces

$$ \require{color} \left.x\right|_{x\gets\colorbox{yellow}{$+2+h$}} $$