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64 lines
2.8 KiB
64 lines
2.8 KiB
5 years ago
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# TypeScript coding guide
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[TypeScript](http://www.typescriptlang.org) is a superset of JavaScript that greatly helps building large web
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applications.
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Coding conventions and best practices comes from the
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[TypeScript guidelines](https://github.com/Microsoft/TypeScript/wiki/Coding-guidelines), and are also detailed in the
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[TypeScript Deep Dive Style Guide](https://basarat.gitbooks.io/typescript/content/docs/styleguide/styleguide.html).
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In addition, this project also follows the general [Angular style guide](https://angular.io/guide/styleguide).
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## Naming conventions
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- Use `PascalCase` for types, classes, interfaces, constants and enum values.
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- Use `camelCase` for variables, properties and functions
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- Avoid prefixing interfaces with a capital `I`, see [Angular style guide](https://angular.io/guide/styleguide#!#03-03)
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- Do not use `_` as a prefix for private properties. An exception can be made for backing fields like this:
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```typescript
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private _foo: string;
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get foo() { return this._foo; } // foo is read-only to consumers
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```
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## Ordering
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- Within a file, type definitions should come first
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- Within a class, these priorities should be respected:
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- Properties comes before functions
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- Static symbols comes before instance symbols
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- Public symbols comes before private symbols
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## Coding rules
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- Use single quotes `'` for strings
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- Always use strict equality checks: `===` and `!==` instead of `==` or `!=` to avoid comparison pitfalls (see
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[JavaScript equality table](https://dorey.github.io/JavaScript-Equality-Table/)).
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The only accepted usage for `==` is when you want to check a value against `null` or `undefined`.
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- Use `[]` instead of `Array` constructor
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- Use `{}` instead of `Object` constructor
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- Always specify types for function parameters and returns (if applicable)
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- Do not export types/functions unless you need to share it across multiple components
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- Do not introduce new types/values to the global namespace
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- Use arrow functions over anonymous function expressions
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- Only surround arrow function parameters when necessary.
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For example, `(x) => x + x` is wrong but the following are correct:
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- `x => x + x`
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- `(x, y) => x + y`
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- `<T>(x: T, y: T) => x === y`
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## Definitions
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In order to infer types from JavaScript modules, TypeScript language supports external type definitions. They are
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located in the `node_modules/@types` folder.
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To manage type definitions, use standard `npm install|update|remove` commands.
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## Enforcement
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Coding rules are enforced in this project via [TSLint](https://github.com/palantir/tslint).
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Angular-specific rules are also enforced via the [Codelyzer](https://github.com/mgechev/codelyzer) rule extensions.
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## Learn more
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The read of [TypeScript Deep Dive](https://basarat.gitbooks.io/typescript) is recommended, this is a very good
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reference book for TypeScript (and also open-source).
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