JavaScript & TypeScript

JavaScript

Sample

• Use TypeScript
• Use the latest stable JavaScript syntax with a transpiler, such as babel.
• Use ESLint and Prettier for auto-formatting and auto-fixing
• Use Jest for unit testing
• Prefer ES6 classes over prototypes.
• Use strict equality checks (=== and !==) except when comparing against (null or undefined).
• Prefer arrow functions =>, over the function keyword except when defining classes or methods.
• Prefer ES6 destructuring over object literal notation.
• Use ES6 spread and rest operator wherever possible for a cleaner code.
• Use PascalCase for classes, lowerCamelCase for variables and functions, SCREAMING_SNAKE_CASE for constants, _singleLeadingUnderscore for private variables and functions.
• Prefer template strings over string concatenation.
• Prefer promises over callbacks.
• Prefer array functions like forEach, map, filter and reduce over for/while loops.
• Use const for declaring variables that will never be re-assigned, and let otherwise.
• Avoid var to declare variables.
• Prefer async/await over traditional promise syntax
• Use the Nullish coalescing operator ??

TypeScript

• Use TypeScript in strict mode
• Prefer Functions over Classes
• Use PascalCase for Interfaces and Type Aliases
• Use readonly properties where applicable
• Use const Assertions where applicable to avoid type widening
• Avoid Mixins
• Avoid Decorators
• Avoid Overloading Functions
• Prefer Optional Properties in an interface rather than declaring the property type as T | undefined
• Prefer explicitly defining interfaces over Extending Interfaces
• Avoid the use of the any type
• Avoid the Non-null assertion operator
• Avoid Type Assertions
• Prefer the as-syntax for Type Assertions over the angle-bracket syntax
• Prefer Type Guards over Type Assertions
• Prefer Union Types, Lookup Types, Mapped Types and const Assertions over Enums
• Prefer arrow functions =>, over the function keyword except when using Generics

Formatting

• Use Prettier defaults with the following additional configuration (.prettierrc):

  jsonCopy

  {
    "singleQuote": true
  }
  

  This configuration includes:

  • Use semicolons at the end of each statement (sample)
  • Prefer single quotes (sample)
  • Use a trailing comma after each item in a multi-line array or object literal, including the last item. (sample)

If ESLint is used along with Prettier, the ESLInt plugin eslint-config-prettier should also be used to turn off all ESLint style rules that are already handled by Prettier.