(types/refactor): refactor code into TypeScript

- add a few interfaces for the types
- add a few function signatures
- no .js extension import, and no .ts extension either, TS only
  supports extensionless imports apparently(??)

- no errors or warnings in current (non-strict) config
  - need to specify some `any`s a bit more however

(deps): add mobx + MST to devDeps so that the types work

package.json

@@ -2,9 +2,9 @@
   "name": "mst-persist",
   "version": "0.0.2",
   "description": "Persist and hydrate MobX-state-tree stores",
-  "main": "src/index.js",
+  "main": "dist/mst-persist.esm.js",
   "files": [
-    "src/"
+    "dist/"
   ],
   "scripts": {
     "start": "tsdx watch",
@@ -33,6 +33,8 @@
     "mobx-state-tree": "^3.2.1"
   },
   "devDependencies": {
+    "mobx": "^5.11.0",
+    "mobx-state-tree": "^3.14.0",
     "tsdx": "^0.7.2",
     "typescript": "^3.5.2"
   }

src/asyncLocalStorage.js → src/asyncLocalStorage.ts

@@ -1,4 +1,11 @@
-export const AsyncLocalStorage = {
+interface IAsyncLocalStorage {
+  clear(): Promise<void>
+  getItem(key: string): Promise<string>
+  removeItem(key: string): Promise<void>
+  setItem(key: string, value: string): Promise<void>
+}
+
+export const AsyncLocalStorage: IAsyncLocalStorage = {
   clear () {
     return callWithPromise(window.localStorage.clear)
   },
@@ -13,7 +20,7 @@ export const AsyncLocalStorage = {
   }
 }
 
-function callWithPromise (func, ...args) {
+function callWithPromise (func: Function, ...args: any[]): Promise<any> {
   try {
     return Promise.resolve(func(...args))
   } catch (err) {

src/index.js → src/index.ts

@@ -1,8 +1,18 @@
 import { onSnapshot, applySnapshot } from 'mobx-state-tree'
 
-import AsyncLocalStorage from './asyncLocalStorage.js'
+import AsyncLocalStorage from './asyncLocalStorage'
 
-export const persist = (name, store, options = {}) => {
+export interface IArgs {
+  (name: string, store: object, options?: IOptions): Promise<void>
+}
+export interface IOptions {
+  storage?: any,
+  jsonify?: boolean,
+  readonly whitelist?: Array<string>,
+  readonly blacklist?: Array<string>
+}
+
+export const persist: IArgs = (name, store, options = {}) => {
   let {storage, jsonify, whitelist, blacklist} = options
 
   if (typeof window.localStorage !== 'undefined' && (!storage || storage === window.localStorage)) {
@@ -28,15 +38,15 @@ export const persist = (name, store, options = {}) => {
   })
 
   return storage.getItem(name)
-    .then((data) => {
+    .then((data: any) => {
       const snapshot = !jsonify ? data : JSON.parse(data)
       // don't apply falsey (which will error), leave store in initial state
       if (!snapshot) { return }
       applySnapshot(store, snapshot)
     })
 }
 
-function arrToDict (arr) {
+function arrToDict (arr?: Array<string>): object {
   if (!arr) { return {} }
   return arr.reduce((dict, elem) => {
     dict[elem] = true