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Node.js Best Practices
- EGreg 12y agoVery useful!
- donbronson 12y agoAnyone have more insight into the statement "Avoid closures"? Or rather, an alternative to having private functions?
- manyxcxi 12y agoI interpret 'Avoid closures' as just don't define a function within your function. Private functions are simply functions that haven't been exported and aren't really closures (if we're talking about using a module pattern, at least). Excessive closures can lead to memory leaks. Anonymous closures are a PITA when debugging.
- deleted 12y ago[deleted]
- kansface 12y agoClosures are fine, but avoid seagulls: function() { function() { function() { function() { } } } }
- comrh 12y agoSeagulls?
- bhauer 12y agoFirst I've heard the word used in this context, but I assume it refers to the appearance of the braces forming a 'V' pattern of what look like seagulls.
- deleted 12y ago[deleted]
- prezjordan 12y ago"Seagulls" amazing! I'm used to calling them pyramids of doom, or laser guns.
- possibilistic 12y agoI think this is going to catch on.
- dkarapetyan 12y agoDeeply nested closures are harder to inline and optimize. If you want fast code then the easiest way to accomplish that is with explicitly spelling out everything in the prototype instead of generating closures.
- ufo 12y agoThey mentioned memory leaks as their reasoning. Run the following program in any browser and you will see the memory usage balloon out of control: var theThing = null; function replaceThing(){ var oldThing = theThing; function unused(){ return oldThing } theThing = { longStr: new Array(1000000).join('*'), someMethod: function(){ } }; } setInterval(replaceThing, 1000); V8 (and all other engines I tested) will save the oldThing variable in someMethod's lexical environment record, causing each Thing to keep a reference to the previous Thing, preventing it from being garbage collected. This is despite the fact that the old thing is actually unreachable - someMethod never uses the oldThing variable. For a more detailed explanation, check out the post that I lifted this example from: http://point.davidglasser.net/2013/06/27/surprising-javascript-memory-leak.html http://point.davidglasser.net/2013/06/27/surprising-javascri...
- danneu 12y agoExample of Google's Closure Compiler eliminating the memory leak: var theThing = null; function replaceThing() { theThing = { longStr: Array(1E6).join("*"), someMethod: function() { } }; } setInterval(replaceThing, 1E3); http://closure-compiler.appspot.com/home http://closure-compiler.appspot.com/home
- Kiro 12y agoI'm coding a fairly large application in Node and have never heard of EventEmitter or Streams. Does that mean I'm doing something wrong? The impression I get from the article is that it's such a fundamental patterns that every serious application should use it.
- yazaddaruvala 12y agoWhen you say "fairly large" do you mean "a large web app" on top of Express? If so don't worry about it. If you are doing something less "frameworked". Something like custom (text/audio/video) (processing/compression/analysis). You would probably be reinventing Streams if you're not explicitly using them. Meanwhile, apart from implementing Streams, I can't think of a good usecase for EventEmmiter that isn't already in a framework like Express or Socket.io (Someone please enlighten me).
- jb55 12y agoThey are the two most common node abstractions. You can get by without them but it's pretty important to know about them. Streams are the more important one. Once you embrace streams in your applications a lot of things become easier. For example here's a small script I wrote at work to process some csvs and do stuff with them https://gist.github.com/jb55/0ea6aba86e269f1e526b https://gist.github.com/jb55/0ea6aba86e269f1e526b Needless to say before I knew about streams that program was twice as large and twice as buggy. Also check out substack's stream handbook to learn more, they are really handy.
- passfree 12y agoI have one word: CoffeeScript.
- recursive 12y agopffff, that's not even a word. It's two words stuck together.
- eyko 12y agoRecently I prefer using ES6, and transpiling/compiling/translating (which would be the right word here?) to ES5. Browserify with es6ify has made the workflow quite easy (same as Browserify + coffeescript).
- eyko 12y agoRecently I prefer using ES6, and transpiling/compiling/translating (which would be the right word here?) to ES5. Browserify with es6ify has made the workflow quite easy (same as Browserify + coffeescript).
- general_failure 12y agoJust a few comments: > if (!(this instanceof MyClass)) return new MyClass(); If you really want, just throw an exception and kill the program at compile time. Catch programming errors in testing and not do some magic to 'autocorrect' code. > var localFile = fs.createWriteStream('localFile.tmp'); Always catch 'error's in stream objects. Otherwise, it might thrown an exception at runtime. localFile.on('error', /* do something */) Coding style: In most cases if you write you code properly, you don't need to nest more than 3-4 levels. If it gets deeper split it out into separate functions. Otherwise, it's a perfect job for async.series.
- Touche 12y agoAgree about the instanceof trick. I hate that pattern. I'm not sure if it's done to avoid using "new" or because people legitimately make the mistake.
- jwmerrill 12y agoIt's to avoid using "new".
- aikah 12y ago> It's to avoid using "new". yeah,well one is still using new inside the constructor. it's pretty obvious to me that : 1/ one should read the docs before using an api 2/ capitalized functions are meant to be used as constructors. 3/ If you dont like this pattern,write builders and make them obvious. like Object.create() To me when i design js APIs, I have 2 kind of "templates" : the jQuery "$(o).after(b).get(0)"/underscore "_(object).method().value()" monadic api style that wraps types (like promises) OR The way the DOM is built,more java-ish with builders everywhere ( document.createElement ... ). So I hardly use new anymore. I get that people might make mistake or like Python style OO;but still, I think forcing the "new" in unecessary.
- iLoch 12y agoCant you just "return this;" to avoid using "new"?
- Touche 12y agoNotice something not on the list of best practices: documentation. While Node itself has excellent docs (for the most part), the Node community is terrible about documentation. If you're lucky you'll get a single README.md file with the basics covered. Pick any category of module and there's a good chance the most popular modules have little documentation; certainly nothing close to comprehensive.
- chrisfosterelli 12y agoDo they really need more than a single README.md file? Many of those modules are so small that anything more than a single README of documentation would be excessively verbose. I've never ran into the problem of feeling a module was poorly documented. The especially complex modules usually have more extensive documentation on their website. I'd say there are cases that are terrible or useful documentation for sure, but in general most modules are very good about it from my experience.
- twerquie 12y agoI agree with this. The surface area of most modules is small enough to be covered in a README.md, which is displayed prominently on npmjs.org, github.com and a copy of it is in your ./node_modules folder. As said earlier, the core Node.js framework has great documentation, as do other frameworks such as Mongoose and Express.
- vkjv 12y agoI agree with everything you say except for Mongoose. Mongoose lacks a lot of documentation on the fringe use cases. However, the beauty of open source is that you can just read the code, which, in my experience, is the most reliable documentation.
- Monkeyget 12y agoI want to write a simple node application that fetches an http document and write it to the disk. The only requirement is for the application to print out in plain English if there is one of the following error: * the document doesn't exist * there is a connection error during download * the local file couldn't be opened * an error occured during writing. For any other error(out of memory,...) the program can crash. How do I do that in node? I don't know. The request package only tells me the callback's first parameter is "An error when applicable (usually from http.ClientRequest object)". The fs package only tells me "Event: 'error': Emitted if there was an error when writing or piping data." I only picked error reporting as an example so I could showcase the problem of lack of documentation on the most basic APIs (http get and writing file). By the way the Error Handling article [0] on Joyent's website is absolutely wonderful. Call me old fashioned but how can I use an API that doesn't tell me which function to call, what a function accepts as parameters, what it returns or how it signals error? [0] https://www.joyent.com/developers/node/design/errors https://www.joyent.com/developers/node/design/errors
- pedalpete 12y agoWhen they say 'avoiding closures', how does that relate to functions in your module? Your module is often exported as a function, so are they suggesting that every function be exported? I suspect I'm not understanding the logic behind 'stack based'. Why is it better to have your functions not contain other functions (or is it not be contained?)
- akbar501 12y agoIt appears they are warning about using closures everywhere to avoid memory leaks. > are they suggesting that every function be exported? No. Just export the functions that are used outside of the module. Other functions can be private to the module. > Why is it better to have your functions not contain other functions (or is it not be contained?) 1. It can make the code clearer 2. It eliminates one source of memory leaks 3. It allows the V8 runtime to optimize more of your code. There is a function length limit (including comments) before V8 will no longer optimize a function. module.exports = function fOne() { function fTwo() { } do something... fTwo(); } Can become: function fTwo() { } module.exports = function fOne() { do something... fTwo(); }
- ufo 12y agov8 (and all other JS engines I tested) are kind of stupid when it comes to garbage collection. You can see a detailed explanation of the problem in this blog post: http://point.davidglasser.net/2013/06/27/surprising-javascript-memory-leak.html http://point.davidglasser.net/2013/06/27/surprising-javascri...
- whatthemick 12y agoI'm personally not a huge fan of the eventemitter for cases where an event is only ever emitted once (an sql query is done or similar). For 2.0 of Sequelize we've moved almost the entire codebase to promises and will encourage users to interact with Sequelize with promises.
- wooptoo 12y agoPromises and Events are not mutually exclusive. I can imagine a lot of scenarios where both would make sense. But as you said, it doesn't feel right to overuse the EventEmitter mechanism where it's not really needed.
- pavlov 12y agoNot that long ago, anonymous functions and closures were the height of fashion in every language. Now the recommendation is to name your functions and avoid closures. This brings us right back to what C programmers have been doing with function pointers since forever. Not that this is such a bad thing.
- _random_ 12y ago0. Avoid using it, unless truly necessary.