This is a collection of style guides for Kibana projects. The include guides for the following:

JavaScript
Kibana Project
Html

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, 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.

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:

var foo = 'bar';

Wrong:

var foo = "bar";

Opening braces go on the same line

Your opening braces go on the same line as the statement.

Right:

if (true) {
  console.log('winning');
}

Wrong:

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:

if (err) {
  return cb(err);
}

Wrong:

if (err)
  return cb(err);

Prefer multi-line conditionals

But single-line conditionals are allowed for short lines

Preferred:

if (err) {
  return cb(err);
}

Allowed:

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 when it comes to declaring variables deeper inside a function, just put the declarations wherever they make sense.

Right:

var keys = ['foo', 'bar'];
var values = [23, 42];

var object = {};
while (keys.length) {
  var key = keys.pop();
  object[key] = values.pop();
}

Wrong:

var keys = ['foo', 'bar'],
    values = [23, 42],
    object = {},
    key;

while (keys.length) {
  key = keys.pop();
  object[key] = values.pop();
}

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:

var adminUser = db.query('SELECT * FROM users ...');

Wrong:

var admin_user = db.query('SELECT * FROM users ...');

Use UpperCamelCase for class names

Class names should be capitalized using UpperCamelCase.

Right:

function BankAccount() {
}

Wrong:

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 extension, but unfortunately that cannot be applied to class members, nor is it part of any ECMA standard.

Right:

var SECOND = 1 * 1000;

function File() {
}
File.FULL_PERMISSIONS = 0777;

Wrong:

const SECOND = 1 * 1000;

function File() {
}
File.fullPermissions = 0777;

Magic numbers

These are numbers (or other values) simply used in line in your code. Do not use these, give them a variable name so they can be understood and changed easily.

Right:

var minWidth = 300;

if (width < minWidth) {
  ...
}

Wrong:

if (width < 300) {
  ...
}

Global definitions

Don't do this. Everything should be wrapped in a module that can be depended on by other modules. Even things as simple as a single value should be a module.

Function definitions

Prefer the use of function declarations over function expressions. Function expressions are allowed, but should usually be avoided.

Also, keep function definitions above other code instead of relying on function hoisting.

Preferred:

function myFunc() {
  ...
}

Allowed:

var myFunc = function () {
  ...
};

Object / Array creation

Use trailing commas and put short declarations on a single line. Only quote keys when your interpreter complains:

Right:

var a = ['hello', 'world'];
var b = {
  good: 'code',
  'is generally': 'pretty'
};

Wrong:

var a = [
  'hello', 'world'
];
var b = {"good": 'code'
        , is generally: 'pretty'
        };

Object / Array iterations, transformations and operations

Use native ES5 methods to iterate and transform arrays and objects where possible. Do not use for and while loops.

Use descriptive variable names in the closures.

Use a utility library as needed and where it will make code more comprehensible.

Right:

var userNames = users.map(function (user) {
  return user.name;
});

// examples where lodash makes the code more readable
var userNames = _.pluck(users, 'name');

Wrong:

var userNames = [];
for (var i = 0; i < users.length; i++) {
  userNames.push(users[i].name);
}

Use the === operator

Programming is not about remembering stupid rules. Use the triple equality operator as it will work just as expected.

Right:

var a = 0;
if (a !== '') {
  console.log('winning');
}

Wrong:

var a = 0;
if (a == '') {
  console.log('losing');
}

Only use ternary operators for small, simple code

And never use multiple ternaries together

Right:

var foo = (a === b) ? 1 : 2;

Wrong:

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:

var a = [];
if (!a.length) {
  console.log('winning');
}

Wrong:

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:

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:

if (
  thing instanceof Shape
  && !(thing instanceof Square)
  && thing.size > 10
) {
  console.log('bigger than ten?? Woah!');
}

Name regular expressions

Right:

var validPasswordRE = /^(?=.*\d).{4,}$/;

if (password.length >= 4 && validPasswordRE.test(password)) {
  console.log('password is valid');
}

Wrong:

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:

function isPercentage(val) {
  if (val < 0) return false;
  if (val > 100) return false;

  return true;
}

Wrong:

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:

function isPercentage(val) {
  var isInRange = (val >= 0 && val <= 100);
  return isInRange;
}

Chaining operations

When using a chaining syntax (jquery or promises, for example), do not indent the subsequent chained operations, unless there is a logical grouping in them.

Also, if the chain is long, each method should be on a new line.

Right:

$('.someClass')
.addClass('another-class')
.append(someElement)

d3.selectAll('g.bar')
.enter()
  .append('thing')
  .data(anything)
  .exit()
.each(function() ... )

$http.get('/info')
.then(({ data }) => this.transfromInfo(data))
.then((transformed) => $http.post('/new-info', transformed))
.then(({ data }) => console.log(data));

Wrong:

$('.someClass')
  .addClass('another-class')
  .append(someElement)

d3.selectAll('g.bar')
.enter().append('thing').data(anything).exit()
.each(function() ... )

$http.get('/info')
  .then(({ data }) => this.transfromInfo(data))
  .then((transformed) => $http.post('/new-info', transformed))
  .then(({ data }) => console.log(data));

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:

req.on('end', function onEnd() {
  console.log('winning');
});

Wrong:

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:

setTimeout(function() {
  client.connect(afterConnect);
}, 1000);

function afterConnect() {
  console.log('winning');
}

Wrong:

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 its arguments (docblock) should start with /**, contain a single * at the beginning of each line, and end with */.

Right:

// '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:

// 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) {
  // ...
}

Do not comment out code

We use a version management system. If a line of code is no longer needed, remove it, don't simply comment it out.

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:

function ClassName() {

}

Wrong:

var ClassName = function () {};

Inheritance 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:

// uses a lodash inherits mixin
// inheritance is defined first - it's easier to read and the function will be hoisted
_.class(Square).inherits(Shape);

function Square(width, height) {
  Square.Super.call(this);
}

Wrong:

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 its Super class). This is all that should be done within constructors.

Try to follow the Write small functions rule here too.

Use the prototype

If a method/property can go on the prototype, it probably should.

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:

Square.prototype.doFancyThings = function () {
  var self = this;

  somePromiseUtil()
  .then(function (result) {
    self.prop = result.prop;
  });
}

Wrong:

Square.prototype.doFancyThings = function () {
  somePromiseUtil()
  .then(function (result) {
    this.prop = result.prop;
  }).bind(this);
}

Allowed:

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, 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.

Kibana Style Guide

Things listed here are specific to Kibana and likely only apply to this project

Share common utilities as lodash mixins

When creating a utility function, attach it as a lodash mixin.

Several already exist, and can be found in src/kibana/utils/_mixins.js

Filenames

All filenames should use snake_case and can start with an underscore if the module is not intended to be used outside of its containing module.

Right:

src/kibana/index_patterns/index_pattern.js
src/kibana/index_patterns/_field.js

Wrong:

src/kibana/IndexPatterns/IndexPattern.js
src/kibana/IndexPatterns/Field.js

Modules

Kibana uses WebPack, which supports many types of module definitions.

CommonJS Syntax

Module dependencies should be written using CommonJS or ES2015 syntax:

Right:

const _ = require('lodash');
module.exports = ...;

import _ from 'lodash';
export default ...;

Wrong:

define(['lodash'], function (_) {
  ...
});

Angular Usage

Kibana is written in Angular, and uses several utility methods to make using Angular easier.

Defining modules

Angular modules are defined using a custom require module named ui/modules. It is used as follows:

var app = require('ui/modules').get('app/namespace');

app above is a reference to an Angular module, and can be used to define controllers, providers and anything else used in Angular. While you can use this module to create/get any module with ui/modules, we generally use the "kibana" module for everything.

Private modules

A service called Private is available to load any function as an angular module without needing to define it as such. It is used as follows:

app.controller('myController', function($scope, otherDeps, Private) {
  var ExternalClass = Private(require('path/to/some/class'));
  ...
});

Use Private modules for everything except directives, filters, and controllers.

Promises

A more robust version of Angular's $q service is available as Promise. It can be used in the same way as $q, but it comes packaged with several utility methods that provide many of the same useful utilities as Bluebird.

app.service('CustomService', function(Promise, otherDeps) {
  new Promise(function (resolve, reject) {
    ...
  });

  var promisedFunc = Promise.cast(someFunc);

  return Promise.resolve('value');
});

Routes

Angular routes are defined using a custom require module named routes that remove much of the required boilerplate.

require('ui/routes')
.when('/my/object/route/:id?', {
  // angular route code goes here
});

Html Style Guide

Multiple attribute values

When a node has multiple attributes that would cause it to exceed the line character limit, each attribute including the first should be on its own line with a single indent. Also, when a node that is styled in this way has child nodes, there should be a blank line between the opening parent tag and the first child tag.

<ul
  attribute1="value1"
  attribute2="value2"
  attribute3="value3">

  <li></li>
  <li></li>
  ...
</ul>

Api Style Guide

Paths

API routes must start with the /api/ path segment, and should be followed by the plugin id if applicable:

Right: /api/marvel/v1/nodes Wrong: /marvel/api/v1/nodes

Versions

Kibana won't be supporting multiple API versions, so API's should not define a version.

Right: /api/kibana/index_patterns Wrong: /api/kibana/v1/index_patterns

snake_case

Kibana uses snake_case for the entire API, just like Elasticsearch. All urls, paths, query string parameters, values, and bodies should be snake_case formatted.

Right:

POST /api/kibana/index_patterns
{
  "id": "...",
  "time_field_name": "...",
  "fields": [
    ...
  ]
}

Attribution

This JavaScript guide forked from the node style guide created by Felix Geisendörfer and is licensed under the CC BY-SA 3.0 license.

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JavaScript Style Guide

2 Spaces for indention

Newlines

No trailing whitespace

Use Semicolons

120 characters per line

Use single quotes

Opening braces go on the same line

Always use braces for multi-line code

Prefer multi-line conditionals

Declare one variable per var statement

Use lowerCamelCase for variables, properties and function names

Use UpperCamelCase for class names

Use UPPERCASE for Constants

Magic numbers

Global definitions

Function definitions

Object / Array creation

Object / Array iterations, transformations and operations

Use the === operator

Only use ternary operators for small, simple code

Do not extend built-in prototypes

Use descriptive conditions

Name regular expressions

Write small functions

Return early from functions

Chaining operations

Name your closures

No nested closures

Use slashes for comments

Do not comment out code

Classes/Constructors and Inheritance

Capitalized function definition as Constructors

Inheritance should be done with a utility

Keep Constructors Small

Use the prototype

Handling scope and aliasing this

Object.freeze, Object.preventExtensions, Object.seal, with, eval

Getters and Setters

Kibana Style Guide

Share common utilities as lodash mixins

Filenames

Modules

CommonJS Syntax

Angular Usage

Defining modules

Private modules

Promises

Routes

Html Style Guide

Multiple attribute values

Api Style Guide

Paths

Versions

snake_case

Attribution

Handling scope and aliasing `this`