Rename the extension of multiple files with bash script on Mac and Linux

Sometimes we need to rename the extension of multiple files extension in the current directory. Here some shell script snippets to do that in different cases.

Markdown to MDX

If you want to move from markdown with .md extension to .mdx:

for x in **/*.md; do mv "$x" "${x%.md}.mdx"; done

Javascript to Typescript

If you want to move from a Javascript project with .js files extension to Typescript files with .ts extension:

for x in **/*.js; do mv "$x" "${x%.md}.ts"; done