15 web developer interview questions...
Tags: webdev, programming, javascript, html
Published: 2021-09-05 17:33:22

# Advanced Interview Questions

The following will cover the senior web developer interview questions but I suggest you go through them even if you are a fresher or an intermediate web developer candidate

<img style="border-radius:25px;" src="https://images.pexels.com/photos/5699475/pexels-photo-5699475.jpeg?cs=srgb&dl=pexels-alex-green-5699475.jpg" alt="Advanced Interview Questions">

## 0- What are the types of popup boxes present in JavaScript?

There are **three** types of dialog boxes, which are used in JavaScript:

|  type   | usage                                                         |
| :-----: | :------------------------------------------------------------ |
|  alert  | Presents users with a message and an **OK** button            |
| Confirm | Gives the users a window with **OK** and **Cancel** buttons   |
| Prompt  | Shows the user input, alongside **OK** and **Cancel** buttons |

# Advanced Interview Questions

The following Blog will cover the senior web developer interview questions but I suggest you go through them even if you are a fresher or an intermediate web developer candidate

What are the types of popup boxes present in **JavaScript?**

<br>

### 1- There are **three** types of dialog boxes, which are used in JavaScript

The `<window.onload>` event is not called until a page is completely loaded with the entire styling from CSS and images. The event does add a bit of delay when rendering a web page.

With the `<onDocumentReady>` event, it will wait only till the DOM is initialized and will begin the event action. This ensures to reduce any delays in actions.

## 2- How is type conversion handled in JavaScript?

> - JavaScript supports automatic type conversion. Since it is weakly typed, you can pass a function as an argument into another function easily.

> - This ensures that there are no errors or data type-associated warnings as values get converted to the required data type automatically.

### 3- What is the meaning of the scope of a variable in JavaScript?

**Scope** refers to the accessibility of functions and underlying variables in the running environment. There are two scopes supported in JavaScript:

> - Local scope: Here, values and functions declared inside the same function function can only be accessed within that function and not outside it. Consider the following example:

```js
// Code present here cannot use localVariable
function myFunction() {
  var localVariable = "This is a local variable";
  // Code present here can use localVariable
}
```

> - Global scope: If a variable is declared as global, it can be accessed from anywhere in the application. Consider the following example:

```js
var globalVariable = "This is a Global variable";
// Code present here can use globalVariable
function myFunction() {
  // Code present here can also use globalVariable
}
```

## 4- How are comments used in JavaScript?

JavaScript supports two types of comment insertion in the code. Single-line comments and multi-line comments.

Single-line comment: “//” is used for single-line comment insertion
Example:

`//This is a single-line comment`

Multi-line comment: `/\*\*/” is used to add multi-line comments
Example:

```js
/* This
is a
multi-line
comment*/
```

Coming to the next set of interview questions for web developers, here is a common question for JavaScript.

## 5- What are undefined and undeclared variables in JavaScript?

- Variables that have been declared already but not initialized are known as undefined variables.

> On the other hand, if a variable is being used in a program without being declared, then it is considered as an undeclared variable.

Consider the following example:

```js
var undefVar;
alert(undefVar); // undefined variable
alert(notDeclared); // accessing an undeclared variable
```

## 6- What is the method used to submit forms in JavaScript?

Forms can be submitted easily in JavaScript by calling the following method:

`document.forms[0].submit();`
Here, **Zero 0** denotes the index of the form.

## 7- Why is keyword used a lot in JavaScript?

The `<this>` keyword is used to access the current object present in a program. This object resides inside a method, and the keyword is used for referencing the corresponding variable or object.

## 8- What is the use of the ‘defer’ attribute in JavaScript?

The <defer> attribute is used as a boolean type attribute. It is used to delay the execution of the JavaScript code on a web page until the parser completely loads and initializes the page.

**Example:**

`<script src="/example.js" defer></script>`

## 9- How can you prioritize SEO, maintainability, performance, and security in a web application?

This is a **commonly asked** question in a Web Development interview. Here, the interviewer is trying to assess your understanding of the working environment in the firm you’ve applied for.

**If it is a large firm**, then security will get higher priority over SEO. Whereas, if it is a publication firm, **SEO gets the preference**. A little groundwork about the company should help you answer this question.

The next web developer interview question we will look at is regarding jQuery. Check it out.

## 10- What is the result if a jQuery Event Handler returns false?

> If the jQuery Event Handler returns a boolean false value, it simply means that the event will not execute further and will halt the execution for the particular action it is associated with.

## 11- What is the use of the each() function in jQuery?

> The each() function in jQuery is used to iterate over a set of elements. A function can be passed to the each() method. This will result in the execution of each of the events for which the object has been called.

## 12- What is pair programming?

- **Pair programming** is a scenario where you will be working closely with a colleague on the project, and this is done to help solve the problems at hand. If the development scenario is fast-paced, Agile development might not work efficiently. The interviewer asks this question to see if you can work with other people easily and effectively.

## 12- What is the use of the $() function in jQuery?

> The $() function is used as a wrapper to wrap objects into their jQuery counterparts. This is done to give users the ability to call any method that is defined for the jQuery object.

**Note:** Selectors can also be passed to the $() function, resulting in the output of a jQuery object that contains matched DOM elements.

## 13- What are the advantages of using a content delivery network (CDN) in jQuery?

> CDNs are widely used in jQuery as they offer an ample number of advantages for users.

**CDNs cause a significant reduction in the load** for the server.
They provide large amounts of savings in the bandwidth.
jQuery frameworks load faster due to optimizations.
CDNs have a caching ability that adds to quicker load times.

## 14- List out the advantage of HTTP/2 as compared with HTTP 1.1?

The advantage of HTTP/2 compared to HTTP/1.1 is

- HTTP headers data compression
- Server push technologies
- Over a single TCP connection parallel loading of page elements
- Prioritization of request

## 15- What are the types of CDNs supported in jQuery?

There are two widely used CDNs with jQuery:

**Microsoft**: Used to load from jQuery AJAX CDN

**Google**: Used to load jQuery from the Google libraries API

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