JavaScript Proxy with Storage

By  on  

The JavaScript Proxy API provides a wealth of "magic" within JavaScript, allowing you to use any object as sort of an alias that allows a wall of validation, formatting, and error throwing. Did you know that you could also employ the Proxy API as an abstraction to different types of storage? Whether it's sessionStorage, localStorage, or IndexedDB, you can use a proxy to make the API much easier to work with!

A very basic usage of the Proxy API is as follows:

/*
const proxy = new Proxy({}, {
  get: (obj, prop) => { ... },
  set: (obj, prop, value) => { ... },
  // more props here
});
*/

// This basic proxy returns null instead of undefined if the
// property doesn't exist
const proxy = new Proxy({}, {
  get: (obj, prop) => {
    return prop in obj ? obj[prop] : null;
  }
});

// proxy.whatever => null

The localStorage API is easy enough to use but employing a Proxy allows us to use the familiar object syntax and eventually even swap out the storage type without any other part of your code being effected.

function getStorage(storage, prefix) {
  return new Proxy({}, {
    set: (obj, prop, value) => {
      // obj[prop] = value;
      storage.setItem(`${prefix}.${prop}`, value);
    },
    get: (obj, prop) => {
      // return obj[prop];
      return storage.getItem(`${prefix}.${prop}`);
    },
  });
}

// Create an instance of the storage proxy
const userObject = getStorage(localStorage, "user");

// Set a value in localStorage
userObject.name = "David";

// Get the value from localStorage
const { name } = userObject;

Note: The code above is a very simplistic example -- you'd also want to add methods for deleting from the object, as well as try/catch to prevent storage errors!

You could swap localStorage for sessionStorage and there'd be very little effect on your overall code! If you do use storage in your app, you're likely already using and abstraction, but I love the basic JavaScript object interaction pleasing.

And I'm not the only one that loves this pattern. Firefox DevTools debugger uses this pattern to abstract the IndexedDB API for storing breakpoints, tabs, and other preferences!

Recent Features

  • By
    LightFace:  Facebook Lightbox for MooTools

    One of the web components I've always loved has been Facebook's modal dialog.  This "lightbox" isn't like others:  no dark overlay, no obnoxious animating to size, and it doesn't try to do "too much."  With Facebook's dialog in mind, I've created LightFace:  a Facebook lightbox...

  • By
    5 More HTML5 APIs You Didn’t Know Existed

    The HTML5 revolution has provided us some awesome JavaScript and HTML APIs.  Some are APIs we knew we've needed for years, others are cutting edge mobile and desktop helpers.  Regardless of API strength or purpose, anything to help us better do our job is a...

Incredible Demos

  • By
    CSS :target

    One interesting CSS pseudo selector is :target.  The target pseudo selector provides styling capabilities for an element whose ID matches the window location's hash.  Let's have a quick look at how the CSS target pseudo selector works! The HTML Assume there are any number of HTML elements with...

  • By
    WordPress-Style Comment Controls Using MooTools or jQuery

    WordPress has a nice little effect on the Admin Dashboard where it shows and hides the comment control links when you mouseover and mouseout of the record's container. Here's how to achieve that effect using MooTools or jQuery. The XHTML Notice that we place the links into...

Discussion

    Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!