# Configuration Objects¶

The various components of MathJax, including its input and output processors, its preprocessors, its extensions, and the MathJax core, all can be configured through the config/default.js file, or via a MathJax.Hub.Config() call (indeed, if you look closely, you will see that config/default.js is itself one big call to MathJax.Hub.Config()). Anything that is in config/default.js can be included in-line to configure MathJax.

The structure that you pass to MathJax.Hub.Config() is a JavaScript object that includes name:value pairs giving the names of parameters and their values, with pairs separated by commas. Be careful not to include a comma after the last value, however, as some browsers (namely Internet Explorer) will fail to process the configuration if you do.

The MathJax components, like the TeX input processor, have their own sections in the configuration object labeled by the component name, and using an object as its value. That object is itself a configuration object made up of name:value pairs that give the configuration options for the component.

For example,

MathJax.Hub.Config({
showProcessingMessages: false,
jax: ["input/TeX", "output/HTML-CSS"],
TeX: {
TagSide: "left",
Macros: {
RR: '{\\bf R}',
bold: ['{\\bf #1}',1]
}
}
});


is a configuration that includes two settings for the MathJax Hub (one for showProcessingMessages and one for the jax array), and a configuration object for the TeX input processor. The latter includes a setting for the TeX input processor’s TagSide option (to set tags on the left rather than the right) and a setting for Macros, which defines new TeX macros (in this case, two macros, one called \RR that produces a bold “R”, and one called \bold that puts is argument in bold face).

The config/default.js file is another example that shows nearly all the configuration options for all of MathJax’s components.