JavaScript Style Guide
The style guide for writing JavaScript code in Ride
This is a guide for writing consistent and aesthetically pleasing JavaScript code in Ride projects. These guidelines are generally based on the Node JS Style Guide, with some minor changes made.
Table of contents
Formatting
4 Spaces for indentation
Use 4 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.
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');
}
Keywords should be followed by a space
// Right
if () {
}
switch () {
}
while () {
}
for () {
}
function () {
}
// Wrong
if() {
}
switch() {
}
while() {
}
for() {
}
function() {
}
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();
}
Naming Conventions
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
Note: this convention will change once we've decided how to support ES2015 (which provides the const keyword).
Constants should be declared as regular variables or static class properties, using all uppercase letters.
// Right
var SECOND = 1 * 1000;
function File() {
}
File.FULL_PERMISSIONS = 0777;
// Wrong
const SECOND = 1 * 1000;
function File() {
}
File.fullPermissions = 0777;
Variables
Object / Array creation
Use trailing commas and put short declarations on a single line. Quote all object keys:
// Right
var a = ['hello', 'world'];
var b = {
'good': 'code',
'is generally': 'pretty',
};
// Wrong
var a = [
'hello', 'world'
];
var b = {good: "code"
, is generally: 'pretty'
};
Conditionals
Use the === operator
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');
}
Use single-line ternary operator
The ternary operator should be used on a single line. Use an if statement when the condition becomes too big.
// Right
var foo = (a === b) ? 1 : 2;
// Wrong
var foo = (a === b)
? 1
: 2;
Use descriptive conditions
Any non-trivial conditions should be assigned to a descriptively named variable or function:
// Right
var isValidPassword = password.length >= 4 && /^(?=.*\d).{4,}$/.test(password);
if (isValidPassword) {
console.log('winning');
}
// Wrong
if (password.length >= 4 && /^(?=.*\d).{4,}$/.test(password)) {
console.log('losing');
}
Functions
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;
}
Respect whitespace conventions
Respect the earlier mentioned whitespace conventions, even when naming functions. The function keyword should be followed by a space, a function name however may not.
// Right
function (bar) {
}
function foo(bar) {
}
var foo = function (bar) {
};
foo(1);
// Wrong
function(bar) {
}
function foo (bar) {
}
var foo = function(bar) {
};
foo (1);
Name your closures
Feel free to give your closures a 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);
Method chaining
One method per line should be used if you want to chain methods.
You should also indent these methods so it's easier to tell they are part of the same chain.
// Right
User
.findOne({ name: 'foo' })
.populate('bar')
.exec(function(err, user) {
return true;
});
// Wrong
User
.findOne({ name: 'foo' })
.populate('bar')
.exec(function(err, user) {
return true;
});
User.findOne({ name: 'foo' })
.populate('bar')
.exec(function(err, user) {
return true;
});
User.findOne({ name: 'foo' }).populate('bar')
.exec(function(err, user) {
return true;
});
User.findOne({ name: 'foo' }).populate('bar')
.exec(function(err, user) {
return true;
});
Comments
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.
// Right
// 'ID_SOMETHING=VALUE' -> ['ID_SOMETHING=VALUE', 'SOMETHING', 'VALUE']
var matches = item.match(/ID_([^\n]+)=([^\n]+)/));
// 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.
function loadUser(id, cb) {
// ...
}
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) {
// ...
}
Use JSDoc for code documentation
JSDoc is a standard for writing and generating code documentation. Use it when documenting classes, modules, etc. A full reference can be found here: http://usejsdoc.org/.
/**
* Class representing a point.
*/
class Point {
/**
* Create a point.
* @param {number} x - The x value.
* @param {number} y - The y value.
*/
constructor(x, y) {
// ...
}
/**
* Get the x value.
* @return {number} The x value.
*/
getX() {
// ...
}
/**
* Get the y value.
* @return {number} The y value.
*/
getY() {
// ...
}
/**
* Convert a string containing two comma-separated numbers into a point.
* @param {string} str - The string containing two comma-separated numbers.
* @return {Point} A Point object.
*/
static fromString(str) {
// ...
}
}
Miscellaneous
Object.freeze, Object.preventExtensions, Object.seal, with, eval
Crazy shit that you will probably never need. Stay away from it.
Requires At Top
Always put requires at top of file to clearly illustrate a file's dependencies. Besides giving an overview for others at a quick glance of dependencies and possible memory impact, it allows one to determine if they need a package.json file should they choose to use the file elsewhere.
Getters and setters
Do not use setters, they cause more problems for people who try to use your software than they can solve.
Feel free to use getters that are free from side effects, like providing a length property for a collection class.
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');
}
jQuery
Although jQuery is available in all Ride projects, it's highly encouraged to use it as less as possible. The main reason we provide jQuery is because of some plugins which cannot work without it.
// Right
var nodes = document.querySelectorAll('.selector');
for (i = 0; i < nodes.length; ++i) {
nodes[i].classList.add('active');
}
document.addEventListener('DOMContentLoaded', function onDOMContentLoaded() {
console.log('loaded');
});
// Wrong
var nodes = $('.selector');
nodes.each(function(key, node) {
node.addClass('active');
});
$(document).ready(function onDocumentReady() {
});
Read more about avoiding jQuery here: http://youmightnotneedjquery.com/
Updated less than a minute ago