@alehuo/type-safe-storage v1.0.0

type-safe-storage

Introduction

This library wraps the browser's localStorage and sessionStorage functionality to provide run-time type-checking of the values that are set and get from the sessionStorage and localStorage object.

This library adds a new parameter to the setItem() and getItem() functions which is used to pass an io-ts codec. The codec is used to validate the data coming from and going to the browser's local storage.

Installation

npm install --save @alehuo/type-safe-storage fp-ts@2.9.5 io-ts@2.2.14

Implemented methods

•   setItem(key, value, codec)

•   getItem(key, codec)

•   removeItem()

•   clear()

•   length // getter

Example

setItem & getItem

import { typeSafeLocalStorage as localStorage } from "@alehuo/type-safe-storage";
import * as t from "io-ts";
import { isRight } from "fp-ts/lib/either";

const codec = t.type({
  id: t.number,
  value: t.string,
});

const res = localStorage.setItem(
  "key",
  {
    id: 1,
    value: "First",
  },
  codec
);

// setItem returns either Left<"ERROR"> or Right<"Ok"> depending if the value passes the validation

if (isRight(res)) {
  console.log("Success!");
  const retrieved = localStorage.getItem("key", codec);
  // Returns null for non-existent storage value
  // Returns instance of Left<t.Errors> if the decoding fails
  // Returns Right<{ id: number, value: string }> for a successfull decoding
  if (retrieved === null) {
    console.error("Value does not exist!");
  }
  if (isLeft(retrieved)) {
    console.error("Failed to decode value!");
  } else {
    console.log(`The value is: "${retrieved.right.value}"`);
    // Output: The value is: "First"
  }
}