Question

I’m creating a simple WebGL project and need a way to load in models. I decided to use OBJ format so I need a way to load it in. The file is (going to be) stored on the server and my question is: how does one in JS load in a text file and scan it line by line, token by token (like with streams in C++)? I’m new to JS, hence my question. The easier way, the better.

UPDATE: I used your solution, broofa, but I’m not sure if I did it right. I load the data from a file in forEach loop you wrote but outside of it (i.e. after all your code) the object I’ve been filling data with is “undefined”. What am I doing wrong? Here’s the code:

var materialFilename;

function loadOBJModel(filename)
{
    // ...

    var req = new XMLHttpRequest();
    req.open('GET', filename);
    req.responseType = 'text';
    req.onreadystatechange = function()
    {
        if (req.readyState == 4)
        {
            var lines = req.responseText.split(/\n/g);
            lines.forEach(function(line)
            {
                readLine(line);
            });
        }
    }
    req.send();

    alert(materialFilename);

    // ...
}

function readLine(line)
{
    // ...

    else if (tokens[0] == "mtllib")
    {
        materialFilename = tokens[1];
    }

    // ...
}

Answer 1

You can use XMLHttpRequest to fetch the file, assuming it’s coming from the same domain as your main web page. If not, and you have control over the server hosting your file, you can enable CORS without too much trouble. E.g.

To scan line-by-line, you can use split(). E.g. Something like this …

var req = new XMLHttpRequest();
req.open('GET', '/your/url/goes/here');
req.onreadystatechange = function() {
  if (req.readyState == 4) {
    if (req.status == 200) {
      var lines = req.responseText.split(/\n/g);
      lines.forEach(function(line, i) {
        // 'line' is a line of your file, 'i' is the line number (starting at 0)
      });
    } else {
      // (something went wrong with the request)
    }
  }
}

req.send();