What
Rename every .js file under a directory to .ts in one shell command.
Why
TypeScript checks .ts and .tsx files by default. It can also check JavaScript when you enable allowJs and checkJs, so renaming is only necessary when you want the files converted to TypeScript. Preview the files and check for existing .ts destinations before a bulk rename.
How
find src -name "*.js" -print
find src -name "*.js" -exec sh -c '
for source do
destination=${source%.js}.ts
if [ -e "$destination" ]; then
echo "Skipping $source: $destination already exists" >&2
else
mv "$source" "$destination"
fi
done
' sh {} +