add a save function that both support fs and localstorage

packages/auto-utils/src/index.ts

@@ -1,2 +1,3 @@
 export * from './api'
 export * from './network'
+export * from './save'

packages/auto-utils/src/save.ts

@@ -0,0 +1,23 @@
+export const save = async (key: string, value: any) => {
+  // detect if we are in the browser or in node
+  if (typeof window !== 'undefined') {
+    await saveOnLocalStorage(key, value)
+  } else {
+    await saveOnFileSystem(key, value)
+  }
+}
+
+export const saveOnLocalStorage = async (key: string, value: any) => {
+  if (typeof window !== 'undefined')
+    // save on local storage
+    localStorage.setItem(key, JSON.stringify(value))
+  else throw new Error('This function can only be used in the browser')
+}
+
+export const saveOnFileSystem = async (key: string, value: any) => {
+  if (typeof window === 'undefined') {
+    // save on file system
+    const fs = await import('fs/promises')
+    await fs.writeFile(key, JSON.stringify(value))
+  } else throw new Error('This function can only be used in node')
+}