# 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 = {
tex: {packages: {'[+]': ['require']}}
};


Since the require extension is included in the combined components that contain the TeX input jax, it may already be in the package list. In that case, if you want to disable it, you can remove it:

window.MathJax = {
tex: {packages: {'[-]': ['require']}}
};


## require Options¶

Adding the require extension to the packages array defines a require sub-block of the tex configuration block with the following values:

MathJax = {
tex: {
require: {
allow: {
base: false,
'all-packages': false
},
defaultAllow: true
}
};

allow: {...}

This sub-object indicates which extensions can be loaded by \require. The keys are the package names, and the value is true to allow the extension to be loaded, and false to disallow it. If an extension is not in the list, the default value is given by defaultAllow, described below.

defaultAllow: true

This is the value used for any extensions that are requested, but are not in the allow object described above. If set to true, any extension not listed in allow will be allowed; if false, only the ones listed in allow (with value true) will be allowed.