How Can I Get File Extensions with Javascript?

How can I get file extensions with JavaScript?

Working with file extensions can be a common requirement when dealing with file uploads, file validations, or file management in JavaScript. In this blog post, we will explore different approaches to extract file extensions using JavaScript.

1. Using the split() method

The split() method allows us to split a string into an array of substrings based on a specified separator. By splitting the file name on the dot (.), we can extract the file extension as the last element of the resulting array.

const fileName = 'example.txt';
const fileExtension = fileName.split('.').pop();

console.log(fileExtension); // Output: txt

2. Using the lastIndexOf() method

The lastIndexOf() method returns the index within a string of the last occurrence of a specified value. By finding the last occurrence of the dot (.) in the file name, we can extract the file extension using the substring() method.

const fileName = 'example.txt';
const dotIndex = fileName.lastIndexOf('.');
const fileExtension = fileName.substring(dotIndex + 1);

console.log(fileExtension); // Output: txt

3. Using regular expressions

Regular expressions provide a powerful way to match patterns in strings. By using a regular expression to match the file extension pattern, we can extract the file extension from the file name.

const fileName = 'example.txt';
const fileExtension = fileName.match(/.([^.]+)$/)[1];

console.log(fileExtension); // Output: txt

These are three different approaches to extract file extensions using JavaScript. Depending on your specific use case, you can choose the method that best suits your needs.

Remember to handle edge cases such as file names without extensions or files with multiple dots in their names. Additionally, always validate user input to ensure the file name is in the expected format.

Happy coding!