Sometimes there is only one item in the array list, and array access operator seems to get only the first character of the element in this case. How to fix it?
\documentclass[tikz, border=1cm]{standalone}
\begin{document}
\begin{tikzpicture}
\node at (0, 0) {\pgfmathparse{{0.3}[0]}\pgfmathresult};
\node at (1, 0) {\pgfmathparse{{13}[0]}\pgfmathresult};
\node at (2, 0) {\pgfmathparse{{"abc"}[0]}\pgfmathresult};
\node at (3, 0) {\pgfmathparse{{12pt}[0]}\pgfmathresult};
\end{tikzpicture}
\end{document}

{{"abc"}}[0]. (2) Don't use PGF (or LaTeX in general) for that. – Henri Menke Jun 01 '20 at 09:53