Write a function that takes a string and returns the file extension, which is the string after the last dot (.) in the string. If there is no dot in the string, return empty string.

function extractFileExtension(fileName) {
  // Split the file name into an array of strings at the dot character.
  const splitFileName = fileName.split(".");

  // Check if the split file name array has more than one element.
  if (splitFileName.length > 1) {
    // Get the last element in the array, which is the file extension.
    const fileExtension = splitFileName.pop();

    // Return the file extension.
    return fileExtension;
  }
  // The file name does not have an extension, so return an empty string.
  return "";
}

• The extractFileExtension function takes a string as an argument.
• The split method is used to split the string into an array of strings at the dot character.
• The pop method is used to get the last element in the array, which is the file extension.
• The file extension is returned.

• String.prototype.split()

• GitHub

Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

Please make sure to update tests as appropriate.