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JavaScript → Build A Firebase CRUD App – Part 2

Last modified on May 11th, 2021
Raja Tamil
Firebase Javascript

In this Firebase CRUD JavaScript Web Tutorial, you will be learning how to do CREATE, UPDATE and DELETE operations with Firebase Real-time database using Firebase Functions such as push(), update() and remove().

I will be showing you a simple web app example to demonstrate Firebase JavaScript CRUD operations.

This is the second part of the Firebase CRUD JavaScript Tutorial series.

The first part covers how to get started with Firebase from setting up a project to how to READ data from the Firebase database.

🔥Part #1: Firebase CRUD JavaScript Tutorial → Setup and Read Data

🔥Part #2: Firebase CRUD JavaScript Tutorial → Insert/Update/Delete data (you’re here)

This is the final outcome of this Firebase CRUD JavaScript tutorial.

Add/Insert A New User Data using Firebase

There are three ways to save data to the Firebase Database:

  • Push()
  • Set() and
  • Update()

Push(data, callback):

  • Firebase push() method will insert new data to a given Database reference path. It takes two arguments; one is the actual data that you want to insert and the second is the callback function that will run once the operation is done.
  • This method will create a unique id/key in a given path as a key and it will add the data that we passed as a value of that key.

The image below shows the unique keys added to the given Firebase Database reference path when you use push() method.

Note: As you know, in the first part, I imported JSON data to the Database on the firebase console which is an index-based, like the image below.

I recommend using push unique key because it has a timestamp in it to avoid overwrites when multiple users push() data at the same time.

Here is the starter project that you can download and follow along with me if you wish.

Learn Firebase Storage Quickly [Guide]

1. Add (+) button and  User Form:  Add the following HTML code to your index.html. This HTML code contains a <section> element in which there is a (+) add button and a New User Form.

<!-- add user module -->
<section id="add-user-module"> <button id="open-add-user-form-btn">+</button>
        <h2>Add User</h2> name:<br> <input type='text' data-key='name' class='user-input'><br> age:<br> <input
            type='text' data-key='age' class='user-input'><br> email:<br> <input type='text' data-key='email'
            class='user-input'><br> <button type='button' id="add-user-btn">add user</button>

Inside the Add User Form, I have three <input> fields for name, age, and email and each one contains a class called user-input and an attribute called data-key.  

2. Show the Add User Form when a user hovers (+) button:  I have used CSS style to achieve this using position absolute. Go ahead and copy the code below and paste it into your style.css file.

/* Add User Module */
#add-user-module {
    width: 30px;
    margin-bottom: 1px;
    margin-left: 10px;
    margin-top: 10px;

#add-user-module #open-add-user-form-btn {
    background: #54bb7d;
    font-size: 1.5em;
    color: white;
    padding-bottom: 5px;

#add-user-module form {
    position: absolute;
    padding: 10px;
    width: 150px;
    background-color: #e1e1e1;
    border: 1px solid #999;
    display: none;

#add-user-module form input {
    width: 97%;
    margin: 2px 0;

#add-user-module form button {
    background: #54bb7d;
    font-size: 1em;
    padding: 0px 10px;
    color: white;
    margin-top: 10px;

#add-user-module:hover form {
    display: block;

At this stage, the form should show when you hover the (+) button.

Note: At the top of JavaScript, you need to replace the config object with your own credentials otherwise your app will NOT work.

3. Attach Click Event to the Add User Button: Cache #add-user-btn DOM element which is inside the Add User Form. Then, attach a click event to it with the callback function addUserBtnClicked().

const addUserBtnUI = document.getElementById("add-user-btn"); 
addUserBtnUI.addEventListener("click", addUserBtnClicked);

4. Create a new user Object: Inside the call back function, create a Firebase Database reference path where you want to insert the new user data.

const usersRef = dbRef.child('users');

Then, get all the input fields from the Add User Form and cache them into an array variable addUserInputsUI like so.

const addUserInputsUI = document.getElementsByClassName("user-input");

After that…create an empty JavaScript object in which I am going to store a new user data as key-value pairs.

// this object will hold the new user information 
let newUser = {};

Now, Loop though addUserInputsUI array that has three input fields. Then, inside each iteration, get the value of input attribute data-key and store it into the variable key.

After that… create another variable called value and store it in the actual user typed value.

// loop through View to get the data for the model 
for (let i = 0, len = addUserInputsUI.length; i < len; i++) {
    let key = addUserInputsUI[i].getAttribute('data-key');
    let value = addUserInputsUI[i].value;
    newUser[key] = value;

Assign the key and value variables to the newUser object on each iteration. You will have an object something like this:

    "age": "21",
    "email": "",
    "name": "Raja Tamil"

5.  Push it to the Firebase Database:  Finally, push() method will go ahead and insert the new user data to the Firebase Database in a given path which is in usersRef.

usersRef.push(newUser, function () {
    console.log("data has been inserted");

That’s simple eh!

As you notice, my user list on the browser has been updated automatically because I am using a Firebase event called value to get a list of users.

The cool thing about value event is that it’s triggered whenever there is a change that could be Add, Delete or Edit in the database reference that this event runs on. If you want to learn more about queries, you can check out How To Query, Filter And Sort Firebase Real-Time Database.


Recommended Full Video Course
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Edit /Update An Existing User Data

You can either use Update() or Set() to make any change to an existing user data.

Let’s take a look at Update() first…

Update(data, callback):

• You can make changes to one or more values of a user using update(). For example, If I want to update just a name, I can do it without affecting other keys such as name and age.

• What happens if I send an object that has a key which is not in the Firebase Database? Well, the cool thing about the update() method is, whenever there is a key match, this method will update the value of it.

• If there is no key match, then update() method will insert it in as a new key.

On the other hand,

Set(data, callback):

set() method will replace everything in a given Firebase Database Reference path. For example, if the javascript object that you’re going to update, has the only {name: “raja”}, set() method will overwrite everything in that specific path and all other keys will be deleted. It’s kind of dangerous because you may lose data without knowing.

• If you want to intentionally change any user object value to be null, set() method would be great for it.

Let’s get the edit user functionality working…

1. Edit User Form: Add the below HTML code for Edit User Form to index.html file. This form is very similar to Add User Form except for one extra hidden input field with the class name edit-userid, which is used to set and get the user id.

<!-- edit user module -->
<section id="edit-user-module">
        <h2>Edit user</h2> <input type="hidden" class="edit-userid"> name:<br> <input type='text' data-key='name'
            class='edit-user-input'><br> age:<br> <input type='text' data-key='age' class='edit-user-input'><br>
        email:<br> <input type='text' data-key='email' class='edit-user-input'><br> <button type='button'

2. Make Edit Form Pretty: Add the CSS code below to the style.css. As you can see, I use display: none to hide the form initially, then I will use JavaScript to show when a user clicks the edit button which I will add next.
Let’s add the edit button next…

3. Add Edit button: Add Edit icon (✎) inside <li> via JavaScript.

// edit icon 
let editIconUI = document.createElement("span");
editIconUI.class = "edit-user";
editIconUI.innerHTML = " ✎";
editIconUI.setAttribute("userid", key);
editIconUI.addEventListener("click", editButtonClicked) // Append after li.innerHTML = 

Create editIconUI span element, then attach a click event to it with a callback function editButtonClicked().

Make sure to append editIconUI to <li> after appending li.innerHTML, so that the edit icon will be shown after the username text.

4. Show Edit Form with the User Data: Get the Edit User Form DOM element and set the display property to block which makes the Form visible.

// show the Edit User Form 
document.getElementById('edit-user-module').style.display = "block";

Then, assign user id, which you get from the edit button, with an attribute userid to the hidden <input> text field edit-userid. I will have user id available when I click the save button from the Edit From to update the user data later.

//set user id to the hidden input field 
document.querySelector(".edit-userid").value ="userid");

After that, create a Firebase Database reference path to get selected user data by userid.

const userRef = dbRef.child('users/' +"userid"));

Next, create a variable that will have all the input fields from the Edit User Form.

// set data to the user field 
const editUserInputsUI = document.querySelectorAll(".edit-user-input");

Now, I am going to define a firebase event called “value” on the userRef variable. The second argument in that event is a call back function with parameter snap which will have the selected user data.

userRef.on("value", snap => {
    for (var i = 0, len = editUserInputsUI.length; i < len; i++) {
        var key = editUserInputsUI[i].getAttribute("data-key");
        editUserInputsUI[i].value = snap.val()[key];

Inside that callback event, loop through the editUserInputsUI array and get the value of an attribute data-key on each iteration and store it in a variable key. I can assign an appropriate value from snap.val()[key] to the input field.

Note: value Firebase event will return promise as well as a callback. For simplicity’s sake, I am not going to handle the error using callback/promises.

At this stage, a user will be able to see the Edit User Form with selected user data filled in when the edit button is clicked.

5. Save the updated user data on to the Firebase Database: When a user makes some changes and hits the save button, the edited data will be saved to the Firebase database.

To do that, Get a save button and attach a click event to that with the callback function editButtonClicked(). 

const saveBtn = document.querySelector("#edit-user-btn"); 
saveBtn.addEventListener("click", saveUserBtnClicked)

As you can see, I have created saveBtn and attached a click event with the callback function saveUserBtnClicked. 

Inside the callback function, create a variable that will have the userID value which you can get from the hidden text field.

const userID = document.querySelector(".edit-userid").value;

Then, create a database reference where you want to update the new changes

const userRef = dbRef.child('users/' + userID);

After that, create an empty object that I will store the updated data from the user input fields.

var editedUserObject = {}

Get all the <input> fields from Edit User Form and store them in an array editUserInputsUI. 

const editUserInputsUI = document.querySelectorAll(".edit-user-input");

Now, Loop though editUserInputsUI array and in each iteration gets the value from the <input> attribute data-key and store it in the key variable and get the user typed value from <input> field and store in the variable value.

editUserInputsUI.forEach(function (textField) {
    let key = textField.getAttribute("data-key");
    let value = textField.value;
    editedUserObject[textField.getAttribute("data-key")] = textField.value

Then, assign the key and value variables to the editedUserObject object on each iteration.

Now, you will have an object that is ready to update.

Finally, user update() method.

One more thing I need to do for usability purposes is to hide the Edit User Form when a user clicks the save button.

document.getElementById('edit-user-module').style.display = "none";

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Delete/Remove Data

remove(data, callback)

The remove() method will remove everything from a given database reference path. It takes two arguments, one is the data in this case user id and the callback function that will run once the delete operation is completed.

If you want to keep the userid and remove all the data inside it, you could use set() to replace with null.

1. Add a Delete Icon to the <li>

// delete icon 
let deleteIconUI = document.createElement("span");
deleteIconUI.class = "delete-user";
deleteIconUI.innerHTML = " ☓";
deleteIconUI.setAttribute("userid", key);
deleteIconUI.addEventListener("click", deleteButtonClicked) 

Similar to the Edit Icon, append delete icon after li.innertHTML line, so that the delete icon will be on the right side.

2. deleteButtonClicked(): Inside this callback function, I use e.stopPropagation() that will stop clicking the <li> when you click the delete button it called Event Bubbling.

function deleteButtonClicked(e) {
    const userID ="userid");
    const userRef = dbRef.child('users/' + userID);

Then, get the user id that you want to get rid of from the delete button using userid attribute.

Next, create a database path reference where you want to remove the data from.

Finally, invoke remove() method on userRef.

That’s it.

In conclusion

Congratulations, You have successfully completed the Firebase CRUD JavaScript/js tutorial by creating a simple User Web App with the CRUD operations.

Along the way I also showed you the value Firebase Event and as well as Firebase methods such as Push, Set and Update and their differences.

You can find the full source code here.

Let me know what kind of application you are going to build with Firebase and JavaScript!

Feel free to comment below if you have any questions about what you have learned or any suggestions.

UP NEXT🔥 How To Query, Filter And Sort Firebase Real-Time Database