I need to serve your page using the same server that is serving the data; localhost:3000 not working

[Jerry Wiltz]

I am working through a D3 example where I have to read a data.csv file with it.

I have downloaded and set up Node.js, next I have created a server with this code, and it works great.

var http = require('http');

var fs = require('fs');

var server = http.createServer(function(request, response){

response.writeHead(200, {

'Content-Type' : 'text-html'

});

fs.readFile('data.csv', 'utf8', function (err, text ){

response.end(text);

});

});

server.listen(3000, function () {

console.log('Server is listening at http://localhost:3000');

});

But .. this does not work. d3.csv does not like it, or there is some browser issue, or something else.

<script>

d3.csv("http://localhost:3000", function (myArrayOfObjects){

myArrayOfObjects.forEach(function (d){

console.log(d.x + ", " + d.y);

});

    });

</script>

For this situation, this what I get from the Chrome Console:

XMLHttpRequest cannot load http://localhost:3000/. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access.

[Japhy Bartlett]

Here's a SO post about this:

https://stackoverflow.com/a/18643011

the quick version is, your server needs to set a 'Access-Control-Allow-Origin' header, probably something like:

```
response.writeHead(200, {
'Content-Type' : 'text-html',

'Access-Control-Allow-Origin': '*',
});
```

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[Jerry Wiltz]

Thanks Japhy,

I tried that. But it did not work. I think I have to install/enable CORS as well along with that.

Is this correct?

Jerry

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[Gordon Woodhull]

CORS is the name of the mechanism, and this is the usual way to enable it.

https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS

I'd advise looking at the response headers for the ajax request in your browser's developer tools, and make sure that header was really added.

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[Jerry Wiltz]

I was able to make this work by:

The first thing was getting the right MIME for the request, it is supposed to be 'text/csv' and the link for that is:
https://github.com/d3/d3-3.x-api-reference/blob/master/CSV.md

The second was was for the access control origin setting which was here:
https://stackoverflow.com/questions/18642828/origin-http-localhost3000-is-not-allowed-by-access-control-allow-origin/18643011#18643011

Thank You

Jerry

[Jerry Wiltz]

Thank you Gordon, that helped me.

Jerry