Now, just open your browser and load - voilà, you should get a lovely "Hello World" greeting.
#Yahoo finance vbscript webscraper code code#
If you have Node.js installed, all you need to do is save the code to the file MyServer.js and run it in your shell with node MyServer.js. The only thing we have to pay attention to here is to return swiftly and not block the function itself, but it's hard to do that, as almost all standard calls are asynchronous (either via callbacks or Promises) - just make sure you don't run while (true) 😀īut enough of theory, let's check it out, shall we? Whenever a client sends a request, Node.js will parse it in the background and call our anonymous function and pass the request object. That is because we still have a callback registered via createServer (the function we passed). In this case, however, we don't have to deal with thread management and we always stay with one thread, thanks to callbacks and the event loop.Īs mentioned, listen will return immediately, but - although there's no code following our listen call - the application won't exit immediately. At this point, the latest, we'd have to switch to multi-threading, as otherwise we could handle exactly one connection at a time. In most other languages, we'd usually have an accept function/method, which would block our thread and return the connection socket of the connecting client. The fact that listen is not a blocking call, but returns immediately.
The handler function we pass to createServer.
There are two interesting bits here and both already hint at our event loop and JavaScript's asynchronicity: Finally, we listen on the specified port - and that's actually it. Here, we import the HTTP standard library with require, then create a server object with createServer and pass it an anonymous handler function, which the library will invoke for each incoming HTTP request. Let's check that quickly out with a simple web server example:Ĭonst server = http. As opposed to how many languages handle concurrency, with multi-threading, JavaScript has always only used a single thread and performed blocking operations in an asynchronous fashion, relying primarily on callback functions (or function pointers, as C developers may call them). Now, it could easily open network connections, store records in databases, or even just read and write files on your hard drive.Įssentially, Node.js introduced JavaScript as a server-side language and provides a regular JavaScript engine, freed from the usual browser sandbox shackles and, instead, pumped up with a standard system library for networking and file access.
#Yahoo finance vbscript webscraper code full#
Contrary to the browser environment, it did not have any more access to a browser window or cookie storage, but what it got instead, was full access to the system resources. NodeJS took Chrome's JavaScript engine and brought it to the server (or better the command line). However that changed when Ryan Dahl introduced NodeJS in 2009. And for more than a decade, JavaScript was really mostly confined to that use case and to the browser. JavaScript was originally meant to add rudimentary scripting abilities to browsers, in order to allow websites to support more custom ways of interactivity with the user, like showing a dialog box or creating additional HTML content on-the-fly.įor this purpose, browsers are providing a runtime environment (with global objects such as document and window) to enable your code to interact with the browser instance and the page itself. Understanding NodeJS: A brief introduction
Whether it's a web or mobile application, JavaScript now has the right tools. JavaScript has become one of the most popular and widely used languages due to the massive improvements it has seen and the introduction of the runtime known as NodeJS.
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