require
The require extension defines the non-standard \require macro
that allows you to load extensions from within a math expression in a
web page. For example:
\(\require{enclose} \enclose{circle}{x}\)
would load the enclose extension, making the following
\enclose command available for use.
An extension only needs to be loaded once, and then it is available for all subsequent typeset expressions.
This extension is already loaded in all the components that
include the TeX input jax, other than input/tex-base. To load the
require extension explicitly (when using input/tex-base for
example), add '[tex]/require' to the load array of the
loader block of your MathJax configuration, and add 'require'
to the packages array of the tex block.
window.MathJax = {
loader: {load: ['[tex]/require']},
tex: {packages: {'[+]': ['require']}}
};