Today we will be looking at how we can use localStorage to save form fields and use this feature to prefill forms or send the data to API for further processing!

Local Storage or Session Storage

Modern browsers provide storage APIs that enable browsers to save data locally and provide offline/cache mechanisms to web sites. This reduces the need to send data to server and then retrieve it back, let’s say for form prefilling feature. Thus reducing the traffic load.

There are ,primarily, three kinds of storage types available:

  • localStorage
  • sessionStorage
  • Cookies
Local Storage:

Local storage stores value in simple key-value pairs. Data is always stored in strings. The data is accessible to all pages of the domain and remains persistent even after the browser is closed.

Session Storage:

Session storage also stores value in simple key-value pairs, and is stored in strings. The data is accessible to all pages of the domain, but data is deleted on browser close. Data is accessible for the window/tab session only


Cookies are the ubiquitious files stored by websites in the browser. Cookies send data back to server for every HTTP request thus increasing the amount of traffic between client and server.

Accessing Local Storage

Browser storage in Chromium based browsers like Edge and Chrome, Storage module is available under the Application tab. However, in Firefox and Safari, it is located under the Storage tab.

To store data in local storage, you need to use the ’localStorage.setItem(‘myKey’, data)’ method where ‘myKey’ is the key under which data is available, and ‘data’ is the actual data you want to store. To access the data, you need to use the ’localStorage.getItem(‘myKey’)’ method. The ‘myKey’ is the key that you have used to store data

Using the localStorage API

//Declare a variable
let data = 'Data that I want to store!'

//Setting data in localStorage 
localStorage.setItem('dataKey', data);

//Get data from localStorage
let savedData = localStorage.getItem('dataKey') 
console.log(savedData); //Output: 'Data that I want to store!'

//Remove data from localStorage

Using the sessionStorage API

//Declare a variable
let data = 'Data that I want to store!'

//Setting data in localStorage 
sessionStorage.setItem('dataKey', data);

//Get data from localStorage
let savedData = sessionStorage.getItem('dataKey') 
console.log(savedData); //Output: 'Data that I want to store!'

//Remove data from localStorage
Using local storage API to create auto save forms

Objective: To create forms for a web app when reloaded automatically prefills the data. We are going to use two methods : with form data and without form data. The FormData() constructor creates a FormData object which is populated with the form’s current key-value pairs using the name property of each element for keys and their submitted value for the values.

Here’s a basic form with the id ‘withoutFormData’ and few fields. Each file has been provided a id

    <form id = "withoutFormData">
        <div class="form-group">
            <label class="sr-only">Full name</label>
            <input type="text" class="form-control input-lg" placeholder="Full name" id = "wfd_name">
        <div class="form-group">
            <label class="sr-only">Username</label>
            <input type="text" class="form-control input-lg" placeholder="Username" id = "wfd_username">
        <div class="form-group">
            <label class="sr-only">E-mail</label>
            <input type="email" class="form-control input-lg" placeholder="E-mail" id = "wfd_email">
        <button type="submit" class="btn btn-lg btn-primary">
            Sign Up
        <div id = "notification"></div>

We then assign the form to a variable.

//Get the form element
let form = document.querySelector('#withoutFormData');

//Assign a prefix for saving the data in localStorage
let prefix = 'autosave_';

//set the item to local storage in the inputHandler event
//using the localStorage.setItem method

function inputHandler(event){

//save the field to a variable
    let field =;

//Only save if the field has an id
    if(! return;

//Save the field to local storage using the prefix and field id as key
// and the value from field value
    localStorage.setItem(prefix +, field.value)

//Clear saved data from local storage
    function clearStorage(){

    //Get all the fields in the form
    let fields = form.elements;

    //Loop through each field and remove it from storage
    for (let field of fields){
        localStorage.removeItem(prefix +;

//load the saved item from local storage 
//using localStorage.getItem method

function loadSaved() {

    //use the form elements property to 
    //get all the fields inside the form
    let fields = form.elements;

    //Loop through each one and load saved data 
    //from storage using a for...of loop
    for(let field of fields){
        let field = localStorage.getItem(prefix +
        if(!saved) continue;
        field.value = saved;

    //Load saved data from storage

/*Listen for DOM Events using event delegation method
* on the form element and pass in a named function 
* to run as callback function 

//listen for input
form.addEventListener('input', inputHandler);
//listen for submit


Head over to the Playground to check out the project. Don’t forget to open the debug logs.

That is all for this blog post. Leave me a line on to share some JavaScript basics that you might be interested in sharing.