JavaScript Answers

How to append to innerHTML without destroying descendants’ event listeners with JavaScript?

When you use innerHTML to set HTML content, it completely replaces the existing content, including any event listeners attached to descendant elements.

To append content without destroying event listeners on existing elements, you have a few options:

1. Using insertAdjacentHTML()

This method allows you to insert HTML into the DOM at a specified position relative to the element.

2. Creating new elements and appending them

Instead of manipulating HTML strings directly, you can create new DOM elements using document.createElement() and append them to the existing elements.

To use this, we write:

// Using insertAdjacentHTML()
var container = document.getElementById('container');
container.insertAdjacentHTML('beforeend', '<div>New Content</div>');

// Creating new elements and appending them
var newDiv = document.createElement('div');
newDiv.textContent = 'New Content';

Both of these methods allow you to append content without destroying event listeners on existing elements.

Choose the one that best fits your use case and coding style.

JavaScript Answers

How to detect if a browser is blocking a popup with JavaScript?

Detecting whether a popup has been blocked by the browser using JavaScript can be tricky because most modern browsers do not provide a direct API for such detection due to privacy and security concerns.

However, you can use a workaround to infer whether the popup has been blocked or not.

One common approach is to open the popup and then check if it was successfully opened or not.

If it wasn’t, it’s likely that the browser blocked it.

Here’s how you can do it:

function openPopup(url, name, width, height) {
    // Open the popup
    var popup =, name, 'width=' + width + ',height=' + height);

    // Check if the popup was successfully opened
    if (popup) {
        // Popup was opened successfully
        console.log('Popup opened successfully');
    } else {
        // Popup was blocked
        console.log('Popup was blocked by the browser');

In this code, the function attempts to open a popup window with the specified URL, name, width, and height.

If the browser allows the popup, it returns a reference to the newly opened window. Otherwise, it returns null.

By checking the value returned by, we can infer whether the popup was blocked or not.

However, note that this method has limitations and may not always accurately detect if the popup was blocked.

Some browsers, for example, may silently block popups without returning null from

Additionally, some browsers may have popup blockers disabled, or the user may have configured exceptions for certain sites.

So, while this method can provide some indication, it’s not foolproof, and it’s important to consider alternative approaches if accurate detection is crucial for your application.

JavaScript Answers

How to use HTML as the view engine in Express with JavaScript?

In Express.js, by default, the view engine is set to use a template engine such as EJS, Handlebars, Pug (formerly Jade), etc.

However, if you want to use plain HTML files as your views without any template engine, you can do so by configuring Express to use the html file extension and serve static HTML files.

Here’s how you can set up Express to serve static HTML files as views:

1. Install Express

If you haven’t already installed Express in your project, you can do so using npm:

npm install express

2. Set up your Express app

Create your Express app and configure it to serve static HTML files from a directory.

const express = require("express");
const app = express();

// Set the directory from which to serve static HTML files

// Set the view engine to use HTML files
app.set("view engine", "html");

// Set the directory where your HTML files are stored
app.set("views", __dirname + "/views");

// Define your routes
app.get("/", (req, res) => {
  // Render the 'index.html' file

// Start the server
const PORT = process.env.PORT || 3000;
app.listen(PORT, () => {
  console.log(`Server is running on port ${PORT}`);

3. Create your HTML files

Create HTML files in a directory specified in the views directory.

For example, if you set app.set('views', __dirname + '/views');, create an index.html file in the views directory.

4. Accessing HTML files

Your HTML files will be served as views when you access the routes defined in your Express app.

For example, accessing the root route (/) will render the index.html file.

Your directory structure might look like this:

│   app.js
    │   index.html

In this setup, Express will serve static HTML files from the views directory without any additional processing. You can use plain HTML, CSS, and JavaScript in your HTML files as needed.

Angular Answers

How to add background-image using ngStyle with Angular and TypeScript?

In Angular, you can use the ngStyle directive to apply dynamic styles to an element.

To add a background image using ngStyle, you’ll need to bind a style property to an expression in your component’s TypeScript code.

In your component’s TypeScript file (e.g., app.component.ts), define a variable to hold the background image URL:

import { Component } from '@angular/core';

  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
export class AppComponent {
  backgroundImageUrl = 'url_to_your_image.jpg';

In your component’s HTML file (e.g., app.component.html), use the ngStyle directive to apply the background image dynamically:

<div [ngStyle]="{'background-image': 'url(' + backgroundImageUrl + ')'}">
  <!-- Your content here -->

This code binds the background-image style property to the backgroundImageUrl variable defined in the component class.

Make sure to replace 'url_to_your_image.jpg' with the actual URL or path of your background image.

Alternatively, if you want to specify the background image URL directly in the template without using a component variable, you can do it like this:

<div [ngStyle]="{'background-image': 'url(\'path/to/your/image.jpg\')'}">
  <!-- Your content here -->

Remember to escape the single quotes within the URL string using backslashes (\') if the URL is specified directly in the template.

JavaScript Answers

How to stop CKEditor from automatically stripping classes from div with JavaScript?

To stop CKEditor from automatically stripping classes from <div> elements, you can configure CKEditor to allow certain HTML tags and attributes, including classes.

This can be achieved by configuring the CKEditor instance to use a specific set of allowed content rules.

For example, we write:

// Assuming you have already initialized CKEditor
var editor = CKEDITOR.replace('editor', {
    // Define the allowed content rules
    // Here we allow <div> elements with any class attribute
    // You can customize this as needed
    extraAllowedContent: 'div(*){*};',
    // Disable content filtering
    // Note: Disabling content filtering may pose security risks, 
    // so use it carefully and consider implementing server-side filtering
    // or other security measures
    allowedContent: true

In this example, extraAllowedContent allows you to specify additional elements and attributes that CKEditor should allow.

In this case, we’re allowing <div> elements with any class attribute.

allowedContent is set to true to disable content filtering completely.

Be cautious when using this option, as it can potentially allow malicious content to be injected into the editor.

Make sure to adjust the extraAllowedContent option according to your specific needs and security considerations.