Defining Macros in MathJax

In case of malfunction of other methods, one needs to include macros' configurations separately from another environment configuration. Also use "\\" instead of "\" to escape. For instance,

<script type="text/x-mathjax-config;executed=true">
MathJax.Hub.Config({
  tex2jax: {inlineMath: [['$','$'], ['\\(','\\)']]}
});
MathJax.Hub.Config({
  TeX:{
      Macros: {
        p :'{\\mathcal{P}}',
        np :'{\\mathcal{NP}}'
      }
  }
});
</script>

Test

$$\p =? \np$$