TypeError: "size" argument must be a number

I am new to javascript, and while following a tutorial I came across this code:

const fs = require ('fs')

function readCallback(err, data){
    console.log('file read')
}

function copyAll(srcFiles, dest, callback){
    for (let i=0; i < srcFiles.length; ++i){
        fs.read(srcFiles[i], readCallback)
    }
    console.log('ending copyAll')
    callback()
}

copyAll(['a.txt', 'b.txt', 'c.txt'], 'test', () => console.log('All done'))

console.log('Entering event loop')

However I get the following error message when I run the code:

C:\Users\Syed Hassaan Hasan\Desktop\Assignmnet 2 (AP)>node example.js
buffer.js:113
    throw err;
    ^

TypeError: "size" argument must be a number
    at Function.Buffer.allocUnsafe (buffer.js:140:3)
    at Object.fs.read (fs.js:658:21)
    at copyAll (C:\Users\Syed Hassaan Hasan\Desktop\Assignmnet 2 (AP)\example.js:9:6)
    at Object.<anonymous> (C:\Users\Syed Hassaan Hasan\Desktop\Assignmnet 2 (AP)\example.js:15:1)
    at Module._compile (module.js:570:32)
    at Object.Module._extensions..js (module.js:579:10)
    at Module.load (module.js:487:32)
    at tryModuleLoad (module.js:446:12)
    at Function.Module._load (module.js:438:3)
    at Module.runMain (module.js:604:10)

Can somebody please tell me what am I doing wrong and what do I need to learn in order to resolve these errors?

via Hassaan Hasan