# 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']}}
    };

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.

## require Commands

The require extension implements the following macros: `\require`