How to Read a Local Text File?

Question

I’m trying to write a simple text file reader by creating a function that takes in the file’s path and converts each line of text into a char array, but it’s not working.

function readTextFile() {
  var rawFile = new XMLHttpRequest();
  rawFile.open("GET", "testing.txt", true);
  rawFile.onreadystatechange = function() {
    if (rawFile.readyState === 4) {
      var allText = rawFile.responseText;
      document.getElementById("textSection").innerHTML = allText;
    }
  }
  rawFile.send();
}

What is going wrong here?

This still doesn’t seem to work after changing the code a little bit from a previous revision and now it’s giving me an XMLHttpRequest exception 101.

I’ve tested this on Firefox and it works, but in Google Chrome it just won’t work and it keeps giving me an Exception 101. How can I get this to work on not just Firefox, but also on other browsers (especially Chrome)?

Accepted Answer

You need to check for status 0 (as when loading files locally with XMLHttpRequest, you don't get a status returned because it's not from a Webserver)

function readTextFile(file)
{
    var rawFile = new XMLHttpRequest();
    rawFile.open("GET", file, false);
    rawFile.onreadystatechange = function ()
    {
        if(rawFile.readyState === 4)
        {
            if(rawFile.status === 200 || rawFile.status == 0)
            {
                var allText = rawFile.responseText;
                alert(allText);
            }
        }
    }
    rawFile.send(null);
}

And specify file:// in your filename:

readTextFile("file:///C:/your/path/to/file.txt");

Answer 2

After the introduction of fetch api in javascript, reading file contents could not be simpler.

reading a text file

fetch('file.txt')
  .then(response => response.text())
  .then(text => console.log(text))
  // outputs the content of the text file

reading a json file

fetch('file.json')
  .then(response => response.json())
  .then(jsonResponse => console.log(jsonResponse))     
   // outputs a javascript object from the parsed json

Must Read

Update 30/07/2018 (disclaimer):

This technique works fine in Firefox, but it seems like Chrome's fetch implementation does not support file:/// URL scheme at the date of writing this update (tested in Chrome 68).

How to Read a Local Text File?

22 Answers

Must Read

Update 30/07/2018 (disclaimer):

Alexander Ross