What distinguishes the memory utilization of these two arrays in JavaScript?

In my array, the elements are indexed consecutively with a gap of 1 between each index.

let noGap = [];
noGap[0] = 0;
noGap[1] = 1;

On the other hand, I have a separate array where the indexes are much more spread out.

let gap = [];
gap[0] = 0;
gap[1000] = 1;

I'm curious about the difference in memory usage between the variables noGap and gap. When logged in Chrome console, gap shows a wider length: (1001) [0, undefined × 999, 1].

If indeed gap consumes more memory, I wonder if this increase is directly proportional to the number of undefined values in the array or if it remains constant regardless.

Apologies if this question has been asked before. The closest answer I found was on this page, but I couldn't fully grasp the explanation provided.

javascriptarraysmemoryundefined

Answer №1

When dealing with sparse arrays in V8, there is a noticeable impact on memory usage. This difference becomes more pronounced as the array grows longer. It's interesting to note that once an array reaches around 1000 elements, V8 adjusts its internal representation for sparse arrays. If the array continues to lengthen, it is likely to consume a similar amount of memory.

I recently conducted some informal memory analysis using the Chrome dev tools and discovered the following results. The table below shows the relationship between the length of a sparse array and the corresponding memory consumption:

| sparse array length | retained size |
|---------------------|---------------|
| 1                   | 56            |
| 10                  | 304           |
| 1000                | 12,184        |
| 2000                | 184           |
| 3000                | 184           |
| 3000, less sparse   | 472           |

It can be observed that memory usage increases proportionally with array length up to 1000 elements. However, beyond this point, the pattern changes significantly, with memory consumption becoming more dependent on the number of initialized indices.

My theory is that V8 transitions from storing all values within the range of indices 0 to length (as seen in a 1000-element array) to utilizing a hash map that only includes entries for defined indices.

Please note that these observations are based on my own experimentation and not on any official documentation regarding V8 implementation details.

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

The font family specified in the Materia UI theme is experiencing compatibility issues on browsers that are not Chrome

Having difficulty overriding some elements with a specific font, as it seems to work perfectly on Chrome but not on other browsers like Safari and FireFox. Could there be something overlooked? Below is the code snippet: const customTheme = createMuiTheme( ...

javascriptcssfontsmaterial-uimaterial-design

Disregard the instructions upon loading the page

I've implemented a directive to automatically focus on the newest input field added to my page. It works well, but there is one issue - when the page loads, the last input is selected by default. I want to exclude this behavior during page load and in ...

javascripthtmlangularjs

Animating a group of images with JQuery

Hey there! I've been working on a simple animation for my webpage, but I'm having some trouble getting it to work the way I want. You can check out my page at . What I'm trying to achieve is having each image appear at its final position an ...

javascriptjqueryhtmlcssjquery-animate

Tips for retrieving data from a Node.js server with a POST request in a React application

I'm currently working on a MERN authentication project, but I've hit a roadblock. Whenever the information is submitted on my register page, it triggers an add user function on the front end. async function addUser(user) { const config = { ...

javascriptnode.jsreactjsexpressaxios

lengthy conditional statement in JavaScript

Is there a more efficient way to handle a long series of if-else statements in JavaScript? I'm not experienced enough with the language to optimize this code. Any suggestions or guidance would be greatly appreciated. $('#webform-component-primar ...

javascriptjqueryif-statementrefactoring

Displaying the Array内容

I received an array from the function $site->latestBookmarks() that looks like this: Array ( [0] => Array ( [url] => http://support.apple.com/kb/HT1343 [title] => Mac OS X Keyboard Shortcuts ) [1] => Array ( [url] => http://stuffkit.com/ ...

phparraysprintingecho

How to retrieve the clicked value using jQuery within a jinja2 loop

I'm currently working on an app that utilizes a Flask backend and Jinja2 templating. Within the HTML, I have a loop set up to organize data into batches, creating three columns on the web page: {% for batch in df.iterrows() | batch(3) %} <d ...

javascriptjqueryhtml-listsjinja2

Transact-SQL: Array of JSON

I am trying to save the output of an API query in JSON format to a SQL Server 2016 table. Currently, I am having trouble transforming the JSON output. Here is what I have tried: When I execute this code: DECLARE @J NVARCHAR(MAX) = '{"c":[4. ...

arraysjsonsql-servert-sql

When I try to hover my mouse over the element for the first time, the style.cursor of 'hand' is not functioning as expected

Just delving into the world of programming, I recently attempted to change the cursor style to hand during the onmouseover event. Oddly enough, upon the initial page load, the border style changed as intended but the cursor style remained unaffected. It wa ...

javascripthtmlcss

Apply various filters to extract and refine information from the database

I have successfully retrieved data from the database. The structure of the data is as follows: serie --- title (string) --- category (array) To filter the data, I have implemented a search filter using a computed property. This is how it looks: f ...

javascriptarraysvue.jsfilteringvuetify.js

Implementing color with JavaScript by utilizing RGB input boxes

I am currently working on a project where I am attempting to change the color of a text area based on RGB values entered into input boxes. However, I am facing some challenges getting the values to apply correctly. Below is the code snippet I am working wi ...

javascriptjqueryinputcolorstextarea

The Find() method in Mongoose and Node.js might return undefined

I recently encountered an issue while working on a simple function in Node.js and Mongoose that should return true if the model is empty. Even though my mongoose configuration seemed perfectly fine: var mongoose = require('mongoose'); var db = ...

javascriptnode.jsmongodbmongoosefind

"Using jQuery to selectively hide a div and eliminate the required field

Is there a way to remove the "required" attribute from hidden fields while keeping it required in visible fields? In this form created with Django framework, I need the required field to be removed when a specific option is selected. For instance, if the ...

javascriptjquerydjangodjango-forms

Guide to automatically filling in a form's fields with information from a database by clicking on a link

Currently, I have a form in HTML that is designed to gather user/member information. This form connects to a database with multiple columns, with two key ones being "user_email" and "invoice_id". Upon the page loading, the input for "user_email" remains hi ...

javascriptjquerymysqldatabaseforms

Generating a fresh array of unique objects by referencing an original object without any duplicates

I can't seem to figure out how to achieve what I want, even though it doesn't seem too complicated. I have an array of objects: { "year": 2016, "some stuff": "bla0", "other stuff": 20 }, "year": 2017, "some stuff": "bla1", ...

javascriptjson

The window.Print() function is currently experiencing a glitch in Microsoft Edge (Version 91.0.864.59) when trying to use it for the first time within an Angular 12

If you encounter the issue, please follow these steps using the latest version 91.0.864.59 of the Edge browser: https://stackblitz.com/edit/angular-ivy-zbvzap?file=src/app/app.component.html Click on the print button. Close the print dialog. Click on the ...

javascriptangularprintingmicrosoft-edge

Switching an Array to JSON with the help of SwiftyJSON

Seeking a simple solution to convert a 2-dimensional array into JSON format. I am currently using SwiftyJSON but have run into some difficulties (I'm more of a hardware person, haha). Your assistance is greatly appreciated! import UIKit import Swift ...

arraysjsonswift

Receiving numerous data via $.ajax is not successful

I have successfully implemented a sortable ordered list using nestedSortable. However, I am encountering an issue when trying to add additional data to the ajax request. var sorted = $('ol.sortable').nestedSortable("serialize"); var dataUrl = {} ...

jqueryajaxarraysobjectserialization

Discover the best methods for accessing all pages on a Facebook account

I attempted to retrieve a list of all Facebook pages, but encountered an error. The error message states: 'request is not defined.' Here is the code snippet: var url = 'https://graph.facebook.com/me/accounts'; var accessToken = req.u ...

javascriptnode.jsfacebook-graph-api

What could be causing my CSS transitions to fail when using jQuery to add classes?

I'm currently working on a website and I'm facing an issue with the transition not functioning as expected. The problem persists even when the 7.css stylesheet is removed and interestingly, the transition works fine when using window:hover. My a ...

javascriptjquerycsscss-transitions