After three consecutive occurrences of readyState being set to 4, an Ajax error was triggered by an alert

I encountered a peculiar situation.

If you try double clicking on "Insane" on this fiddle, you will observe that the onreadystatechange function is triggered 3 times, all with readyState = 4. To me, this seems quite bizarre.

What's even more surprising is that when I eliminate the alert(added) from the double click event listener function as depicted in this fiddle, then everything works fine.

Can anyone provide an explanation for this phenomenon? It's truly perplexing to me. Thank you in advance. :)

Answer №1

The reason for this issue is due to the asynchronous nature of your XMLHttpRequest along with the fact that your alert('added') function pauses the JavaScript execution thread before the XMLHttpRequest begins to trigger onreadystatechange. When you close the alert, the XMLHttpRequest has already finished and the four calls to onreadystatechange are waiting in the stack to be executed.

As a result, since the XMLHttpRequest has already completed, .readyState and .status are already set to 4 and 200 respectively. This causes the if statements within each onreadystatechange call to evaluate as true.

To resolve this behavior, you can either make the XMLHttpRequest execute synchronously or move the alert('added') function before invoking the AJAX request. By making these adjustments, you will receive the expected number of alerts:

Check out this link for demonstration

For further information about JavaScript events, timing, and single-threaded processing, refer to the following resource:

Click here to learn more!

Answer №2

A straightforward approach is to incorporate the alert within a function that checks the readyState before displaying it. Here's an example:

function checkReadyState() {
    if (xmlHttpRequest.readyState !== 4) {
        return;
    }
    alert("Ready state is equal to 4.");
    // Additional code can be added here
}

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

Basic issue with jQuery ajax functionality

I am attempting to utilize jQuery's ajax method, however, I am only getting the error callback when making the call. $('form').submit(function() { $.ajax({ url: this.action, data: $(this).serialize(), type: &apos ...

asp.net-mvc ajax jquery

Having trouble with Bootstrap v4 dropdown menu functionality?

For some reason, I cannot get the dropdown menu to work in my Bootstrap v4 implementation. I have tried copying and pasting the code directly from the documentation, as well as testing out examples from other sources on separate pages with no luck. &l ...

javascript html css

Use the column name instead of the index with Jquery's eq() function

Looking for a way to use a static column name in jQuery to get the 5th column text in a table and change the text of a textbox $('textbox').val($(e.target).closest("tr").find('td:eq(4)').text()); If the index of the columns is changed ...

javascript jquery

The dynamic pages specified by the graphql query in the gatsby-node.js file are not being generated by Gatsby.js as expected

Even after running gatsby clean followed by npm run develop, the issue persists... Several individuals familiar with the Gatsby framework have reviewed my gatsby-node.js file, but the problem remains puzzling... Below is a snippet of my gatsby-node.js fi ...

javascript node.js reactjs

Using Javascript to automate the organization of links based on predefined criteria is an

Picture This: A digital library full of categorized links, totaling 1000 in number. Diverse themes are covered by these links, making it a treasure trove of information. Displayed prominently at the top are buttons labeled ALL, MOBILE, CARS, BOOKS, and TE ...

javascript ajax jquery dynamic

Sluggish Performance Noticed with Angular's Ng-If Directive

I have a scenario where I am using an ng-if directive to hide an element until a specific condition is met. Despite the condition being met in my controller, the element does not seem to be in the DOM when I try to locate it with a jQuery selector. It seem ...

javascript jquery angularjs

A guide on incorporating a Java loop with Selenium automation

// Searching and deleting process driver.findElement(By.cssSelector("input[type='search']")).sendKeys("Diversification Rule Template"); driver.findElement(By.className("delete-template")).click(); Alert alert = driver.switchTo.alert(); Thread. ...

javascript java selenium

The functionality of the React Router DOM seems to be malfunctioning

I am facing an issue with running a program on my computer while it runs successfully on other PCs. When I try to run this program, I encounter the following error message. Any help in fixing this would be greatly appreciated... index.js import React, {C ...

javascript reactjs npm react-router react-router-dom

jQuery's AJAX functionality may not always register a successful response

Below is the code snippet I am currently working with: $(".likeBack").on("click", function(){ var user = $(this).attr("user"); var theLikeBack = $(this).closest(".name-area").find(".theLikeBack"); $.a ...

javascript jquery ajax

Is there a way to connect cell values to correspond in Google Sheets?

I have a spreadsheet on Google Sheets containing financial data from companies' statements. This includes both quarterly and annual information, with a dropdown cell at the top allowing me to choose between "Annual" and "Quarterly" data. However, scro ...

javascript excel database google-apps-script google-sheets

Using Vue.js for real-time price calculations

Currently, I'm in the process of creating a hotel booking application and focusing on the booking feature. Within this step, users are able to modify their preferred room type, number of adults, and number of children using a selection box. To clari ...

javascript vue.js vuejs2 vue-component

From declaring variables locally to accessing them globally in JavaScript

I'm facing an issue with JavaScript, webRTC, and Kurento that I can't seem to resolve on my own. My problem arises when trying to store the remote stream from a local variable into a global variable. I'll explain the steps leading to the iss ...

javascript callback stream webrtc kurento

Problems with Google Maps Event Tracker

I recently inherited a section of code that utilizes the Google Maps API to place markers on a map along with information windows. Below is an excerpt from the code responsible for creating the markers and setting up event listeners: if(markers.length > ...

javascript php jquery google-maps

Ways to conceal a particular tab when switching to a different tab

My goal is to have a modal display a date/time set by another party when opened by the user. However, I also want to provide an option for the user to propose a new time in the footer so that they can request a different meeting time from the other party ( ...

javascript html css bootstrap-4

Loop over JSON data using JQuery

I am struggling to extract color names and hex values from JSON data obtained from an external source. Despite creating a jsfiddle to troubleshoot, I am stuck as I can't even trigger the alert('hi'); function. Ideally, I need a list of color ...

javascript jquery json

How to hide the header on a specific page using Angular

Currently, I am working on an Angular project and my requirement is to hide the header block specifically on the login page. Despite attempting to hide the header on the login page, it seems that my efforts have been unsuccessful so far. Is there anyone wh ...

javascript angularjs angular-ui-router angularjs-routing

Exploring the Mechanics of JQuery's when.done Feature

I'm having a tough time grasping the concept of the when...done jQuery event and how it works. Here is a jsFiddle I put together to illustrate the issue. I have two JavaScript functions, Main & subMain. The sequence of events I expect to see on th ...

javascript jquery

Using Ajax.BeginForm, the entire page content can be seamlessly replaced with a partial

I'm encountering difficulties while using Ajax.BeginForm() in my basic ASP.NET MVC project. Despite searching on SO for solutions, nothing I found has resolved the issue at hand. To provide some context, I set up a new project utilizing the default V ...

ajax asp.net-mvc razor

Is there a way to undo the click event in Javascript?

Is there a way to revert back to the initial position after clicking? I successfully changed the x icon to a + icon on click, but now I'm struggling to reverse that action. I've tried using MOUSEUP and DBLCLICK events, but they aren't ideal ...

javascript events

Eliminate spaces within a string using JavaScript

In my quest for knowledge about trimming strings in JavaScript, I came across this intriguing discussion with a regex-based solution. After learning from the thread, I was under the assumption that trim would eliminate the space between "Hello" and "World ...

javascript html trim

JavaScripter Q&A