Reading Files

The simplest way to read a file in Node.js is to use the fs.readFile() method, passing it the file path, encoding and a callback function that will be called with the file data (and the error):

const fs = require('fs');

fs.readFile('/Users/joe/test.txt', 'utf8', (err, data) => {
    if (err) {
        console.error(err);
        return;
    }
    console.log(data);
});

Alternatively, you can use the synchronous version fs.readFileSync():

const fs = require('fs');

try {
    const data = fs.readFileSync('/Users/joe/test.txt', 'utf8');
    console.log(data);
} catch (err) {
    console.error(err);
}

Both fs.readFile() and fs.readFileSync() read the full content of the file in memory before returning the data.

This means that big files are going to have a major impact on your memory consumption and speed of execution of the program.

In this case, a better option is to read the file content using streams.