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Takeaways:
- The Python module SimpleHTTPServer defines a very simple HTTP server in the directory in which the command line command is run
- If the SimpleHTTPServer finds an index.html file in the folder it is run in, then it serves that, otherwise it returns the directory structure of the folder
- D3 includes an XHR module, d3.xhr, that creates an asynchronous request for the URL passed into it and has an option to take in a mimType and a JavaScript Callback Function
- On top of the D3 XHR module site several kinds of type-specific XHR calls that allow for requesting and parsing of specific data
- The D3 Type-Specific XHR Requests are d3.text, d3.json, d3.xml, d3.html, d3.csv, and d3.tsv
- The D3 XHR Requests need a URL where the data they are requesting lives
- Depending on the D3 Type-Specific XHR Requests used, the data will be sent for, received, and then parsed into an array of JavaScript Objects
- For safety, D3 converts all numerical values received from the XHR request into strings
- If an error occurs in the D3 XHR Requests, then the XMLHttpRequest Object will describe in great detail what error it encountered and the data argument will be returned as undefined
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