VS Code snippet transform: convert camel case to Pascal case or vice versa

gistfile1.txt

// If you want to convert a PascalCase variable to camelCase, you can do the following:
// Where `n` is the tab stop you want to reference
${n/^(.)(.*)$/${1:/downcase}${2}/}

// Example: ${1:This is my original} => ${1/^(.)(.*)$/${1:/downcase}${2}/}


// If you want to convert a camelCase variable to PascalCase, you can do the following:
// Where `n` is the tab stop you want to reference
${n/^(.)(.*)$/${1:/upcase}${2}/}

// Example: ${1:This is my original} => ${1/^(.)(.*)$/${1:/upcase}${2}/}

Answer to vscode snippet transform file name in the snippet to camel case or pascal case variable

given file_name_foo.ext file

${TM_FILENAME_BASE/^(.*)_foo$/${1:/pascalcase}/}  ==> FileName
${TM_FILENAME_BASE/^(.*)_foo$/${1}/}  ==> file_name
${TM_FILENAME_BASE/^(.*)_foo$/${1:/upcase}/}  ==> FILE_NAME

:/camelcase works as well.