Node.js Filesystem I/O Asynchronously Read from Files
Example
Use the filesystem module for all file operations:
const fs = require('fs');
With Encoding
In this example, read hello.txt from the directory /tmp. This operation will be completed in the background and the callback occurs on completion or failure:
fs.readFile('/tmp/hello.txt', { encoding: 'utf8' }, (err, content) => {
// If an error occurred, output it and return
if(err) return console.error(err);
// No error occurred, content is a string
console.log(content);
});
Without Encoding
Read the binary file binary.txt from the current directory, asynchronously in the background. Note that we do not set the 'encoding' option - this prevents Node.js from decoding the contents into a string:
fs.readFile('binary', (err, binaryContent) => {
// If an error occurred, output it and return
if(err) return console.error(err);
// No error occurred, content is a Buffer, output it in
// hexadecimal representation.
console.log(content.toString('hex'));
});
Relative paths
Keep in mind that, in general case, your script could be run with an arbitrary current working directory. To address a file relative to the current script, use __dirname or __filename:
fs.readFile(path.resolve(__dirname, 'someFile'), (err, binaryContent) => {
//Rest of Function
}
