59 lines
2.4 KiB
Markdown
59 lines
2.4 KiB
Markdown
# WebStorage Decorators
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A Javascript library that adds property decorators to sync a class property with the local or session storage.
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## Quick Setup
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1. Install with: `npm install --save webstorage-decorators`
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2. Add the decorator to your property and use as normal!
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```typescript
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import {LocalStorage, SessionStorage} from 'webstorage-decorators';
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export class MyCustomClass {
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@LocalStorage({key: 'site_theme', default: 'light_theme'}) theme: string;
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@SessionStorage({encryptWith: config.entryptionKey}) thisUser: User;
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constructor() {
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console.log(this.theme, localStorage.getItem('theme')); // Output: 'light_theme', 'light_theme'
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console.log(this.user, localStorage.getItem('user')); // Output: null, undefined
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user = {first: 'John', last: 'Smith', ...}
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console.log(this.user, this.user == localStorage.getItem('user')); // Output: {first: 'John', last: 'Smith', ...}, true
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}
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}
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```
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## Caveats
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### Custom Functions
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You can technically store anything inside local/session storage however everything is serialized using javascript's JSON,
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so anything extra (prototypes, functions, etc) will be lost. However if you provide a default value, it will be copied &
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the data injected, giving you a workaround to accessing static properties.
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```typescript
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class Person {
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constructor(public first: string, public last: string) { }
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fullName() { return `${this.last}, ${this.first}`; }
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}
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LocalStorage.setItem('example', '{"first": "John", "last": "Smith"}');
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@LocalStorage(null) example!: Person;
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console.log(example.fullName()) // ERROR: fullName function doesn't exist
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LocalStorage.setItem('example2', '{"first": "John", "last": "Smith"}');
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@LocalStorage(new Person(null, null)) example2!: Person;
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console.log(example.fullName()) // Will work because we have a default object to figure out type
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```
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### Impure Functions
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Impure functions don't use the Object's setter preventing the storage from being updated. To prevent this use a pure
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function or save it manually by reading the variable. (Reading triggers change detection & save if there are differences)
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```typescript
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@LocalStorage([1, 2]) example: number[];
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example.push(3) // Impure & won't update storage
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console.log(localStorage.getItem('example')) // Output: [1, 2];
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example; // Trigger save
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console.log(localStorage.getItem('example')) // Output: [1, 2, 3];
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// OR
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example = example.concat([3]); // Pure function requires you to use the setter triggering automatic saving
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```
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