Odd/Even fancy headers with article class

Question

Using fancyhdr and the book class, one can set different headers/footers for odd/even pages as

\fancyhdr[RO]{foo}
\fancyhdr[LE]{bar}

and so on. How can I achieve the same with an article class, where things are not two sided?

Answer 1

The article class defaults to a simple oneside document. You can load it with the twoside option

\documentclass[twoside]{article}

\usepackage{fancyhdr}
\fancyhead[LE,RO]{foo}
\fancyhead[LO,RE]{bar}
\pagestyle{fancy}
\usepackage{lipsum}

\begin{document}

\lipsum
\lipsum
\lipsum

\end{document}