Javascript's Fetch API is usually used to get data from an API. But it can also be used to retrieve files!

Fetch a .txt file

The Response object that is returned from 'fetch', has a few methods that let you retrieve the data returned from the request

• .json(): returns json
• .text(): returns a string of all the text in the response

We use the .text() method to get a string of the text from a file.

fetch('example.txt')
.then(response => response.text()) 
.then(textString => {
    console.log(textString);
});

The process is identical if we wanted to retrieve a .csv file and do something with the data that's in the file. But we have some extra code to break up the file into rows.

fetch('example.csv')
.then(response => response.text()) 
.then(csvString => {
    //Split the csv into rows
    const rows = csvString.split('\n');
    for (row of rows) {
    //Split the row into each of the comma separated values
        console.log(row.split(","));
    }
});

Look at this GitHub repo for example code:
https://github.com/jpowell96/readFilesWithFetch