[Tex/LaTex] how to add number to the title of sections and subsection using the titlesec package

Question

I am using the titlesec package but the numbering of section and subsections disappeared. I need to retrieve it. my code is

\titleformat{\section}[block]{\color{blue}\Large\bfseries\filcenter}{}{1em}{}
\titleformat{\subsection}[hang]{\bfseries}{}{1em}{}    

I need to achive the following specs:
Main headings: Arial, Size 12, Bold, Uppercase, Center Justified.

Sub-headings: Arial, Size 12, Bold, Title case, Left Justified.

Answer 1

You should use \thesection and \thesubsection in the appropriate places; also \MakeUppercase should go in the last argument for \section.

\documentclass{article}
\usepackage{tgtermes,tgheros} % use your preferred ones for the fonts
\usepackage{lipsum} % this is just to produce some text

\usepackage{titlesec}
\titleformat{\section}[block]
  {\fontsize{12}{15}\bfseries\sffamily\filcenter}
  {\thesection}
  {1em}
  {\MakeUppercase}
\titleformat{\subsection}[hang]
  {\fontsize{12}{15}\bfseries\sffamily}
  {\thesubsection}
  {1em}
  {}

\begin{document}

\lipsum[1]

\section{A section title}

\lipsum[2]

\subsection{A subsection title}

\lipsum[3]

\end{document}