From 6230456e6dfc70eaf643cf84c17f523a81351f11 Mon Sep 17 00:00:00 2001 From: Joe Fleming Date: Mon, 15 Sep 2014 14:23:48 -0700 Subject: [PATCH] added style guide, based on node style guide --- STYLEGUIDE.md | 647 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 647 insertions(+) create mode 100644 STYLEGUIDE.md diff --git a/STYLEGUIDE.md b/STYLEGUIDE.md new file mode 100644 index 0000000000000..65d15c3256ccc --- /dev/null +++ b/STYLEGUIDE.md @@ -0,0 +1,647 @@ +This is a collection of style guides for Kibana projects. The include guides for the following: + +- [JavaScript](#javascript-style-guide) +- [Angular](#angular-style-guide) +- [Ruby](#ruby-style-guide) + +# JavaScript Style Guide + +## 2 Spaces for indention + +Use 2 spaces for indenting your code and swear an oath to never mix tabs and +spaces - a special kind of hell is awaiting you otherwise. + +## Newlines + +Use UNIX-style newlines (`\n`), and a newline character as the last character +of a file. Windows-style newlines (`\r\n`) are forbidden inside any repository. + +## No trailing whitespace + +Just like you brush your teeth after every meal, you clean up any trailing +whitespace in your JS files before committing. Otherwise the rotten smell of +careless neglect will eventually drive away contributors and/or co-workers. + +## Use Semicolons + +According to [scientific research][hnsemicolons], the usage of semicolons is +a core value of our community. Consider the points of [the opposition][], but +be a traditionalist when it comes to abusing error correction mechanisms for +cheap syntactic pleasures. + +[the opposition]: http://blog.izs.me/post/2353458699/an-open-letter-to-javascript-leaders-regarding +[hnsemicolons]: http://news.ycombinator.com/item?id=1547647 + +## 120 characters per line + +Try to limit your lines to 80 characters. If it feels right, you can go up to 120 characters. + +## Use single quotes + +Use single quotes, unless you are writing JSON. + +*Right:* + +```js +var foo = 'bar'; +``` + +*Wrong:* + +```js +var foo = "bar"; +``` + +## Opening braces go on the same line + +Your opening braces go on the same line as the statement. + +*Right:* + +```js +if (true) { + console.log('winning'); +} +``` + +*Wrong:* + +```js +if (true) +{ + console.log('losing'); +} +``` + +Also, notice the use of whitespace before and after the condition statement. + +## Always use braces for multi-line code + +*Right:* + +```js +if (err) { + return cb(err); +} +``` + +*Wrong:* + +```js +if (err) + return cb(err); +``` + +## Prefer multi-line conditionals + +But single-line conditionals are allowed for short lines + +*Preferred:* + +```js +if (err) { + return cb(err); +} +``` + +*Allowed:* + +```js +if (err) return cb(err); +``` + +## Declare one variable per var statement + +Declare one variable per var statement, it makes it easier to re-order the +lines. However, ignore [Crockford][crockfordconvention] when it comes to +declaring variables deeper inside a function, just put the declarations wherever +they make sense. + +*Right:* + +```js +var keys = ['foo', 'bar']; +var values = [23, 42]; + +var object = {}; +while (keys.length) { + var key = keys.pop(); + object[key] = values.pop(); +} +``` + +*Wrong:* + +```js +var keys = ['foo', 'bar'], + values = [23, 42], + object = {}, + key; + +while (keys.length) { + key = keys.pop(); + object[key] = values.pop(); +} +``` + +[crockfordconvention]: http://javascript.crockford.com/code.html + +## Use lowerCamelCase for variables, properties and function names + +Variables, properties and function names should use `lowerCamelCase`. They +should also be descriptive. Single character variables and uncommon +abbreviations should generally be avoided. + +*Right:* + +```js +var adminUser = db.query('SELECT * FROM users ...'); +``` + +*Wrong:* + +```js +var admin_user = db.query('SELECT * FROM users ...'); +``` + +## Use UpperCamelCase for class names + +Class names should be capitalized using `UpperCamelCase`. + +*Right:* + +```js +function BankAccount() { +} +``` + +*Wrong:* + +```js +function bank_Account() { +} +``` + +## Use UPPERCASE for Constants + +Constants should be declared as regular variables or static class properties, +using all uppercase letters. + +Node.js / V8 actually supports mozilla's [const][const] extension, but +unfortunately that cannot be applied to class members, nor is it part of any +ECMA standard. + +*Right:* + +```js +var SECOND = 1 * 1000; + +function File() { +} +File.FULL_PERMISSIONS = 0777; +``` + +*Wrong:* + +```js +const SECOND = 1 * 1000; + +function File() { +} +File.fullPermissions = 0777; +``` + +[const]: https://developer.mozilla.org/en/JavaScript/Reference/Statements/const + +## Object / Array creation + +Use trailing commas and put *short* declarations on a single line. Only quote +keys when your interpreter complains: + +*Right:* + +```js +var a = ['hello', 'world']; +var b = { + good: 'code', + 'is generally': 'pretty' +}; +``` + +*Wrong:* + +```js +var a = [ + 'hello', 'world' +]; +var b = {"good": 'code' + , is generally: 'pretty' + }; +``` + +## Use the === operator + +Programming is not about remembering [stupid rules][comparisonoperators]. Use +the triple equality operator as it will work just as expected. + +*Right:* + +```js +var a = 0; +if (a !== '') { + console.log('winning'); +} + +``` + +*Wrong:* + +```js +var a = 0; +if (a == '') { + console.log('losing'); +} +``` + +[comparisonoperators]: https://developer.mozilla.org/en/JavaScript/Reference/Operators/Comparison_Operators + +## Only use ternary operators for small, simple code + +And **never** use multiple ternaries together + +*Right:* + +```js +var foo = (a === b) ? 1 : 2; +``` + +*Wrong:* + +```js +var foo = (a === b) ? 1 : (a === c) ? 2 : 3; +``` + +## Do not extend built-in prototypes + +Do not extend the prototype of native JavaScript objects. Your future self will +be forever grateful. + +*Right:* + +```js +var a = []; +if (!a.length) { + console.log('winning'); +} +``` + +*Wrong:* + +```js +Array.prototype.empty = function() { + return !this.length; +} + +var a = []; +if (a.empty()) { + console.log('losing'); +} +``` + +## Use descriptive conditions + +Any non-trivial conditions should be assigned to a descriptively named variables, broken into +several names variables, or converted to be a function: + +*Right:* + +```js +var thing = ...; +var isShape = thing instanceof Shape; +var notSquare = !(thing instanceof Square); +var largerThan10 = isShape && thing.size > 10; + +if (isShape && notSquare && largerThan10) { + console.log('some big polygon'); +} +``` + +*Wrong:* + +```js +if ( + thing instanceof Shape + && !(thing instanceof Square) + && thing.size > 10 +) { + console.log('bigger than ten?? Woah!'); +} +``` + +## Name regular expressions + +*Right:* + +```js +var validPasswordRE = /^(?=.*\d).{4,}$/; + +if (password.length >= 4 && validPasswordRE.test(password)) { + console.log('password is valid'); +} +``` + +*Wrong:* + +```js +if (password.length >= 4 && /^(?=.*\d).{4,}$/.test(password)) { + console.log('losing'); +} +``` + +## Write small functions + +Keep your functions short. A good function fits on a slide that the people in +the last row of a big room can comfortably read. So don't count on them having +perfect vision and limit yourself to ~15 lines of code per function. + +## Return early from functions + +To avoid deep nesting of if-statements, always return a function's value as early +as possible. + +*Right:* + +```js +function isPercentage(val) { + if (val < 0) return false; + if (val > 100) return false; + + return true; +} +``` + +*Wrong:* + +```js +function isPercentage(val) { + if (val >= 0) { + if (val < 100) { + return true; + } else { + return false; + } + } else { + return false; + } +} +``` + +Or for this particular example it may also be fine to shorten things even +further: + +```js +function isPercentage(val) { + var isInRange = (val >= 0 && val <= 100); + return isInRange; +} +``` + +## Name your closures + +Feel free to give your closures a descriptive name. It shows that you care about them, and +will produce better stack traces, heap and cpu profiles. + +*Right:* + +```js +req.on('end', function onEnd() { + console.log('winning'); +}); +``` + +*Wrong:* + +```js +req.on('end', function() { + console.log('losing'); +}); +``` + +## No nested closures + +Use closures, but don't nest them. Otherwise your code will become a mess. + +*Right:* + +```js +setTimeout(function() { + client.connect(afterConnect); +}, 1000); + +function afterConnect() { + console.log('winning'); +} +``` + +*Wrong:* + +```js +setTimeout(function() { + client.connect(function() { + console.log('losing'); + }); +}, 1000); +``` + +## Use slashes for comments + +Use slashes for both single line and multi line comments. Try to write +comments that explain higher level mechanisms or clarify difficult +segments of your code. **Don't use comments to restate trivial things**. + +***Exception:*** Comment blocks describing a function and it's arguments (docblock) should start with `/**`, contain a single `*` at the begining of each line, and end with `*/`. + +*Right:* + +```js +// 'ID_SOMETHING=VALUE' -> ['ID_SOMETHING=VALUE', 'SOMETHING', 'VALUE'] +var matches = item.match(/ID_([^\n]+)=([^\n]+)/)); + +/** + * Fetches a user from... + * @param {string} id - id of the user + * @return {Promise} + */ +function loadUser(id) { + // This function has a nasty side effect where a failure to increment a + // redis counter used for statistics will cause an exception. This needs + // to be fixed in a later iteration. + + ... +} + +var isSessionValid = (session.expires < Date.now()); +if (isSessionValid) { + ... +} +``` + +*Wrong:* + +```js +// Execute a regex +var matches = item.match(/ID_([^\n]+)=([^\n]+)/)); + +// Usage: loadUser(5, function() { ... }) +function loadUser(id, cb) { + // ... +} + +// Check if the session is valid +var isSessionValid = (session.expires < Date.now()); +// If the session is valid +if (isSessionValid) { + // ... +} +``` + +## Classes/Constructors and Inheritance + +While JavaScript it is not always considered an object-oriented language, it does have the building blocks for writing object oriented code. Of course, as with all things JavaScript, there are many ways this can be accomplished. Generally, we try to err on the side of readability. + +### Capitalized function definition as Constructors + +When Defining a Class/Constructor, use the function definition syntax. + +*Right:* +```js +function ClassName() { + +} +``` + +*Wrong:* +```js +var ClassName = function () {}; +``` + +### Inhertiance should be done with a utility + +While you can do it with pure JS, a utility will remove a lot of boilerplate, and be more readable and functional. + +*Right:* + +```js +// uses a lodash inherits mixin +// inheritance is defined first - it's easier to read and the function will be hoisted +_(Square).inherits(Shape); + +function Square(width, height) { + Square.Super.call(this); +} +``` + +*Wrong:* + +```js +function Square(width, height) { + this.width = width; + this.height = height; +} + +Square.prototype = Object.create(Shape); +``` + +### Keep Constructors Small + +It is often the case that there are properties that can't be defined on the prototype, or work that needs to be done to completely create an object (like call it's Super class). This is all that should be done within constructors. + +Try to follow the [Write small functions](#write-small-functions) rule here too. + +### Use the prototype + +If a method/property *can* go on the prototype, it probably should. + +```js +function Square() { + ... +} + +/** + * method does stuff + * @return {undefined} + */ +Square.prototype.method = function () { + ... +} +``` + +### Handling scope and aliasing `this` + +When creating a prototyped class, each method should almost always start with: + +`var self = this;` + +With the exception of very short methods (roughly 3 lines or less), `self` should always be used in place of `this`. + +Avoid the use of `bind` + +*Right:* + +```js +Square.prototype.doFancyThings = function () { + var self = this; + + somePromiseUtil() + .then(function (result) { + self.prop = result.prop; + }); +} +``` + +*Wrong:* + +```js +Square.prototype.doFancyThings = function () { + somePromiseUtil() + .then(function (result) { + this.prop = result.prop; + }).bind(this); +} +``` + +*Allowed:* + +```js +Square.prototype.area = function () { + return this.width * this.height; +} +``` + +## Object.freeze, Object.preventExtensions, Object.seal, with, eval + +Crazy shit that you will probably never need. Stay away from it. + +## Getters and Setters + +Feel free to use getters that are free from [side effects][sideeffect], like +providing a length property for a collection class. + +Do not use setters, they cause more problems for people who try to use your +software than they can solve. + +[sideeffect]: http://en.wikipedia.org/wiki/Side_effect_(computer_science) + +# Angular Style Guide + +coming soon... + +# Ruby Style Guide + +coming soon... + +# Attribution + +This Javascript guide forked from the [node style guide](https://github.com/felixge/node-style-guide) created by [Felix Geisendörfer](http://felixge.de/) and is +licensed under the [CC BY-SA 3.0](http://creativecommons.org/licenses/by-sa/3.0/) +license.