This is a guide for writing consistent and aesthetically pleasing MindUp code. It is inspired by what is popular within the community, and flavored with some personal opinions.
This guide was first created by Felix Geisendörfer and is licensed under the CC BY-SA 3.0 license. You are encouraged to fork this repository and make adjustments according to your preferences.
- Use JSHint
- 4 Spaces for indention
- Newlines
- No trailing whitespace
- Use Semicolons
- 80 characters per line
- Use single quotes
- Opening braces
- Method chaining
- Variable declaration
- Error first callback are prefered
- Use lowerCamelCase for variables, properties and function names
- Use UpperCamelCase for class names
- Use UPPERCASE for Constants
- Use the === operator
- Use slashes for comments
- Object.freeze, Object.preventExtensions, Object.seal, with, eval
- Getters and setters
Use JSHint to check your code. JSHint plugins are available for on the fly verification for many editors (emacs, vim, atom, etc.). Some JSHint configuration files are present in the project to make JSHint automatically use it.
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.
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.
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.
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.
Limit your lines to 80 characters. Yes, screens have gotten much bigger over the last few years, but your brain has not. Use the additional room for split screen, your editor supports that, right?
Use single quotes, unless you are writing JSON.
Right:
var foo = 'bar';
Wrong:
var foo = "bar";
Your opening braces go on the same line as the statement.
Right:
if (true) {
console.log('winning');
}
Wrong:
if (true)
{
console.log('losing');
}
If the condition is multiline, open the bracket on the next line.
Right:
if (variable > otherVariable ||
variable <= otherVariable)
{
console.log('winning');
}
Wrong:
if (variable > otherVariable ||
variable <= otherVariable) {
console.log('winning');
}
Also, notice the use of whitespace before and after the condition statement.
You can declare ether one variable per line or many.
Right:
var keys = ['foo', 'bar'];
var values = [23, 42];
var object = {};
while (keys.length) {
var key = keys.pop();
object[key] = values.pop();
}
Also right:
var keys = ['foo', 'bar'],
values = [23, 42],
object = {},
key;
while (keys.length) {
key = keys.pop();
object[key] = values.pop();
}
Prefer to use the error first callback pattern common in node.js code.
Right:
fs.readFile('/foo.txt', function(err, data) {
// If an error occurred, handle it (throw, propagate, etc)
if(err) {
console.log('Unknown Error');
return;
}
// Otherwise, log the file contents
console.log(data);
});
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 ...');
Class names should be capitalized using UpperCamelCase
.
Right:
function BankAccount() {
}
Wrong:
function bank_Account() {
}
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;
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');
}
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');
}
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');
}
Keep your functions short.
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;
}
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');
});
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) {
// ...
}
Crazy shit that you will probably never need. Stay away from it.
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.