What happens to an array element when it becomes null within the realm of JavaScript?

As I work on a complex AJAX control class, I've encountered an interesting question.

For instance, imagine I store all page elements in an array upon initialization.

When a user triggers an AJAX-enabled link, specific parts of the content are replaced by the data retrieved from the AJAX call through subsequent methods.

Now, what if after the AJAX call finishes and replaces nodes in the content section, the previously stored nodes in the array become null or undefined (or some other indication of being inactive)?

When I iterate through the array again, do these elements cease to exist? Or do they still occupy space in their old index, just inaccessible?

It may seem like a trivial question, but I'm essentially trying to understand if there is any form of detection and garbage collection for 'dead' elements in a JavaScript array.

Thanks and best wishes.

Answer №1

In JavaScript, when you have a DOM node stored in an array and then remove it from the DOM (for example, after an AJAX call), the node will still be present in the array, taking up space. You have the option to re-add it to the DOM later.

However, if you decide not to re-add it to the DOM and instead set the array item to null or undefined, and there are no other references to that element, it will be garbage collected and no longer consume space.

Keep in mind that there is a distinction between a JavaScript array and a NodeList or HTMLCollection. NodeList can be obtained by using DOM methods like document.getElementsByTagName. Despite their array-like appearance, NodeLists are 'live', meaning removing a node from the DOM will also remove it from the NodeList.

Answer №2

When a DOM element is deleted from the current page, its references are not immediately set to null. Instead, the element remains in memory until all references to it are removed and the garbage collector collects it.

This allows you to use an array of DOM nodes to potentially restore them if they are removed from their original parent elements.

Similar questions

If you have not found the answer to your question or you are interested in this topic, then look at other similar questions below or use the search

Formik Alert: Update depth limit reached

Currently, I am working on an EDIT formik form that is displayed as a MODAL. The issue arises when the setState function is triggered with setState(true), causing the form to appear without any onClick event. Despite changing onClick={editStory} to onClick ...

javascript reactjs react-hooks next.js formik

Determining the type of index to use for an interface

Imagine having an interface called Animal, with some general properties, and then either be a cat or a dog with corresponding properties. interface Dog { dog: { sound: string; } } interface Cat { cat: { lives: number; } } type CatOrDog = Cat | D ...

javascript typescript

Tips for utilizing the foreach loop in PHP to extract information from a database and display it within a jQuery UI accordion

Does anyone know the best way to implement a foreach loop in PHP to retrieve data from a database and populate it into a jQuery-ui accordion? I've been struggling with this task due to my limited knowledge. My approach involves using jQuery-ui for the ...

php jquery ajax jquery-ui foreach

mention a Vue.js component computed property that points to a specific DOM element

Is there a way to access the DOM element that initiated a method inside a Vue component computed property? For example: <template> <img :src="getUrl" class="image1"/> <img :src="getUrl" class="image2"/> </template> <scri ...

javascript vue.js vuejs2 vue-component

Sending a Php request using AJAX and receiving JSON values

Trying to retrieve values from PHP using AJAX Post. I've researched and found that JSON dataType should be used, but encountering an error: "SyntaxError: JSON.parse: unexpected non-whitespace character after JSON data at line 1 column 72 of the JSON d ...

php jquery arrays json ajax

The transmission of data is not initiated by Ajax

Hey there, So I'm a bit new to Ajax and I've got this PHP script that's working fine. I know I need to upgrade it with PDOs, but I also want to implement Ajax to avoid the reloading and to learn something new. Here's the PHP script: ...

php jquery ajax post

What's the best way to handle variables and numerical calculations within PHP loops when dealing with forms?

I'm currently developing a basic PHP page where users can choose how many numbers they want to add together. After selecting the quantity, they input the numbers on a new page, click a button, and then see the sum displayed. The challenge I'm fa ...

javascript php jquery html ajax

Steps for performing a 'back' action within a div element using jQuery

Within my HTML, I have a div element containing a link. When the user clicks this link, I use AJAX to load new content into the div area. This new content includes a 'back' link that, when clicked, should revert back to the previous content. Cur ...

jquery html ajax

Struggling to make image uploading function with Flask and JQuery

Utilize the code snippet below to submit forms and retrieve a modified version of text from Flask using AJAX and JQuery: from flask import Flask, render_template, request, jsonify app = Flask(__name__) @app.route('/') def index(): return re ...

javascript python jquery ajax flask

Combining multiple API requests using NodeJS

I'm currently experimenting with SteamAPI to enhance my understanding of NodeJS. My aim is to retrieve game information after making an initial request to obtain the player's profile and storing the game IDs in an array. However, I am facing a ch ...

javascript node.js request

Storing information in nested arrays using Node.js and MongoDB

My document structure is as follows: { "_id" : ObjectId("5ab4cc12c773133bae3d8dc9"), "__v" : 19.0, "geoGraphicalFilter" : { "aCountries" : [ { "country" : "Spain", "_id" : ObjectId("5ad49ab21 ...

arrays node.js mongodb mongoose mongodb-query

Issue with D3: Events not triggering transitions

I am currently working on creating a bar chart using D3 in Angular4. // Enter Phase this.chart.selectAll('.bar') .data(this.barData) .enter() .append('rect') .attr('class', 'bar'); // Update Phase let bars ...

javascript jquery css angular d3.js

Run the scripts that are returned from AJAX requests

Here's a helpful tip from Lucian Depold: "Instead of sending JavaScript code from PHP to JS, simply send a JSON object or array and execute each entry using the eval() function." Inside index.php, there is code that runs when the document is ready: ...

javascript php ajax return alert

Is there a problem with evalJSON() causing Simple AJAX JS to work on Safari locally but fail on the server and in Firefox?

I created a script that utilized Prototype's AJAX methods to fetch Twitter data in JSON format, process it, and display it within a div. The script was functioning perfectly during testing on Safari 4.0.3 on an OS 10.6.1 machine. However, when I uploa ...

javascript ajax json twitter prototypejs

Can two controllers be used for the main-app and sub-app with the same URL using angular ui-route?

I have implemented two controllers, 'BaseController' and 'SubController', for my main application and sub-application. Both controllers are configured to point to an empty URL. Below is the configuration for the main application:- ang ...

javascript angularjs routes

What is the best way to integrate AJAX with draggable columns in a Laravel application?

I have successfully integrated draggable functionality for table columns using jQuery Sortable within my Laravel application. I am now facing the challenge of updating the database with the data from these columns through AJAX. Despite researching online ...

javascript php jquery ajax laravel

Identifying the color category based on the color code in the props and displaying JSX output

I am in need of a solution to display colors in a table cell. The color codes are stored in mongodb along with their descriptions. I am looking for a library that can determine whether the color code provided is in RGB or hex format, and then render it acc ...

javascript reactjs mongodb

Angular variable resets to initial value after modification

Currently, I am utilizing ui-router to handle the state management for the admin segment of a project. The admin area includes the ability to browse through various categories. In this category management module, I am working on implementing a breadcrumb l ...

javascript angularjs

Creating a unique custom action button within WooCommerce's order management system that triggers an external API call

I've successfully implemented a function that adds a custom action button to the admin order list, allowing me to verify the payment status with the payment gateway. add_filter( 'woocommerce_admin_order_actions', 'add_custom_order_stat ...

php ajax wordpress woocommerce orders

Redefining the type of an existing function in Typescript: A step-by-step guide

If you're looking for a solution where you can declare an existing function without defining an expression, check out this article: . Rather than creating a new function, the goal is to declare the existing function in a similar manner without using t ...

javascript typescript

JavaScripter Q&A