# configmacros

The configmacros extension provides the `macros` and `environments` configuration options for the `tex` block of your MathJax configuration. This allows you to predefine custom macros end environments for your page using javascript. For example,

    window.MathJax = {
      tex: {
        macros: {
          RR: "{\\bf R}",
          bold: ["{\\bf #1}", 1]
        },
        environments: {
          braced: ["\\left\\{", "\\right\\}"]
        }
      }
    };

defines a macro `\RR` that produces a bold “R”, while `\bold{math}` typesets the `math` using the bold font (see Defining TeX macros for more information). It also creates the `braced` environment that puts `\left\{` and `\right\}` around its contents.

This extension is already loaded in all the components that include the TeX input jax, other than `input/tex-base`. To load the configmacros extension explicitly (when using `input/tex-base` for example), add `'[tex]/configmacros'` to the `load` array of the `loader` block of your MathJax configuration, and add `'configmacros'` to the `packages` array of the `tex` block.

    window.MathJax = {
      loader: {load: ['[tex]/configmacros']},
      tex: {packages: {'[+]': ['configmacros']}}
    };

Since the configmacros 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: {'[-]': ['configmacros']}}
    };

## configmacros Options

The configmacros extension adds a `macros` option to the `tex` block that lets you pre-define macros, and the `environments` option that lets you pre-define your own environments.

macros: {}

  This lists macros to define before the TeX input processor begins. These are name: value pairs where the name gives the name of the TeX macro to be defined, and value gives the replacement text for the macro. The value can be a simple replacement string, or an array of the form [value, n], where value is the replacement text and n is the number of parameters for the macro. The array can have a third entry: either a string that is the default value to give for an optional (bracketed) parameter when the macro is used, or an array consisting of template strings that are used to separate the various parameters. The first template must precede the first parameter, the second must precede the second, and so on until the final which must end the last parameter to the macro. See the examples below.

  Note that since the value is a javascript string, backslashes in the replacement text must be doubled to prevent them from acting as javascript escape characters.

  For example,

      macros: {
        RR: '{\\bf R}',                    // a simple string replacement
        bold: ['\\boldsymbol{#1}',1] ,     // this macro has one parameter
        ddx: ['\\frac{d#2}{d#1}', 2, 'x'], // this macro has an optional parameter that defaults to 'x'
        abc: ['(#1)', 1, [null, '\\cba']]  // equivalent to \def\abc#1\cba{(#1)}
      }

  would ask the TeX processor to define four new macros: `\RR`, which produces a bold-face “R”, and `\bold{...}`, which takes one parameter and sets it in the bold-face font, `\ddx`, which has an optional (bracketed) parameter that defaults to `x`, so that `\ddx{y}` produces `\frac{dy}{dx}` while `\ddx[t]{y}` produces `\frac{dy}{dt}`, and `\abc` that is equivalent to `\def\abc#1\cba{(#1)}`.

environments: {}

  This lists environments to define before the TeX input processor begins. These are name: value pairs where the name gives the name of the environment to be defined, and value gives an array that defines the material to go before and after the content of the environment. The array is of the form [before, after, n, opt] where before is the material that replaces the `\begin{name}`, after is the material that replaces `\end{name}`, n is the number of parameters that follow the `\begin{name}`, and opt is the default value used for an optional parameter that would follow `\begin{name}` in brackets. The parameters can be inserted into the before string using `#1`, `#2`, etc., where `#1` is the optional parameter, if there is one.

  Note that since the before and after values are javascript strings, backslashes in the replacement text must be doubled to prevent them from acting as javascript escape characters.

  For example,

      environments: {
        braced: ['\\left\\{', '\\right\\}'],
        ABC: ['(#1)(#2)(', ')', 2, 'X']
      }

  would define two environments, `braced` and `ABC`, where

      \begin{braced} \frac{x}{y} \end{braced}

  would produce the fraction x/y in braces that stretch to the height of the fraction, while

      \begin{ABC}{Z} xyz \end{ABC}

  would produce `(X)(Z)(xyz)`, and

      \begin{ABC}[Y]{Z} xyz \end{ABC}

  would produce `(Y)(Z)(xyz)`.