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Most Asked Entry Level Front-end Developer Interview Questions

Entry Level Front-End Developer Interview Questions

In today’s scenario, especially the front-end development, the interviewers ask and expect a lot many common questions to be answered by the participants, but some miss the opportunity. Because they don’t understand how it works. In web development, many technologies are covered especially HTML, CSS, JS, ANGULAR, and so on. So, to help you out, we have come up with some of the most important entry-level front-end developer interview questions along with answers. To become a front-end developer, you need to know HTML, CSS, and JS. It doesn’t matter if you don’t know Frontend frameworks but you should know some important functions of these three languages. I can solve your problem as much as possible. If you are a beginner the questions below will be very useful.

After COVID, we have come from online interviews to offline interviews. When you prepare for the interview you should not memorize the questions, you should understand them clearly and understand how they work. Some students are looking for a suitable job after completing their studies online, So let’s see some important entry level front-end developer interview questions.

HTML Interview Questions

What does a Doctype do?

The doctype declaration is the very first thing in your HTML document, before the HTML tag.  The doctype declaration in HTML helps the browser to read your webpage correctly. Therefore, always add a doctype declaration in your HTML document so that the browser knows what type of document to expect. It is not case-sensitive this is a standard way of writing doctype in HTML5. A different version of HTML has a different way of writing <doctype> in HTML. The syntax of the Doctype declaration is  <!DOCTYPE html>.

What’s the difference between standards mode and quirks mode?

The different version of HTML has different ways of defining the doctype. So, the way that we define the <doctype> HTML code in the HTML5 version. HTML5 is the latest version that we are using now, other versions of HTML there are different methods available to define the doctype.

Standard mode

Quirks mode

When you define the doctype HTML in your document the website gets rendered in standard compliance mode. If you don’t define the doctype HTML in your document your web page gets rendered in quirks mode.
In this mode, the browser renders a page that respects all implemented standards.  Quirks mode, which could cause unexpected efforts to your webpage.
When you call the class names and ID names on the page that is with doctype, it is case-sensitive. When you call the class names and ID names on the page that is without doctype, it is not case-sensitive.

What’s the difference between HTML and XHTML?

HTML

XHTML

It is Hypertext Markup Language It is Extensible Hypertext Markup Language.
A root element is not mandatory in HTML. Must have one root element in XHTML.
It is an application of SGML. It is an application of XML.
HTML attributes have been quoted as options. Ex:<font color:#ff0000> XHTML attributes have quotes mandatory. Ex:<font color:#ff0000?>
Attributes values are not significant. Ex: <input type=checkbox checked> Attributes value not important. Ex: <input type=checkbox checked=checked>
It is not case-sensitive tags & attributes can be uppercase or lower as per preference. It is case-sensitive tags & attributes must be in lowercase.

What is a meta tag in HTML?

Metatags are self-closing, we do not need a closing tag. Metatag provides the metadata about the HTML document. The metadata is the information about the data of your HTML web page. So, you can say that the meta tag provides information about the data of your HTML webpage.

Why do we use meta tags on our webpage?

The meta tag is not displayed on the webpage, but it will be machine parsable or you can say that it is machine-readable. So, with the help of this meta tag search engines can pass your data look at your metadata, or even index their web page in their search result. suppose you create a website and you want that your website can be indexed in some search engine then you provide some meta tags. That the search engine can pass the meta tags and index your webpage in their search results. So this is a reason why we use metatags.

How to write meta tags?

You can provide the description of the web page, keywords related to the web page, the author of the webpage, and other metadata. Metatags are always inside a <head> tag. Inside the meta tag, you have to specify two important attributes the ‘name‘ and the ‘content‘. Inside the name, you have to specify the name of the attribute and inside the content, you have to provide the content of the name attribute.

For example:

<head>
 <meta name="description" content="HTML course">
<meta name="keywords" content="HTML, learn html">
<meta name="author" content="sharma">
<meta name="viewport" content="width-device-width, 
initial-scale=1.0">
<meta http="refresh" content="1"> </head>
  1. In this above code, the first metatag is the name that specifies the ‘description‘ and inside the content has to provide the ‘description’ of the webpage.
  2. The second meta tag name is specified as the ‘keywords‘ and in the content attribute, you have to specify what kind of keyword you use in a webpage.
  3. The third meta tag name is specified as the ‘Author‘ and in the content attribute, you have to specify Author’s name.
  4. The fourth meta tag is ‘viewport‘, the viewport is the user-visible area of a web page it varies with the device and will be smaller on a mobile device than on a computer screen. Meta viewport element gives the browser instruction on how to control the page dimension and scaling. The “width-device-width” part set the width of the page to follow the screen width of the device. This varies by device and the “initial-scale = 1.0” field sets the initial zoom level when the page is first loaded by the browser.
  5. And the final meta tag has the ‘HTTP” attribute and gives its value “refresh“, this web page can be refreshed after every second.

CSS Interview Questions

What is the difference between Class and ID in CSS?

ID

Class

IDs are unique identifiers. Classes are grade classifiers.
You have an ID ‘main’ for a paragraph and you cannot use the same ID for another paragraph. You have a paragraph with the class ‘chapter’ and you can use the same class on other paragraphs.
ID is a higher priority than class when it comes to CSS. You can have only one ID per element. Class is a lower priority than ID when it comes to CSS. You can have multiple classes per element.
If you use both ID and Class in an HTML element and style it, the ID’s style will work If you use both ID and class in an HTML element and style it, the class style will not work.

When using ID and class, you should not give the same name, otherwise, it will be confusing. I prefer to use more classes than IDs because you can do anything with classes that you can’t do with IDs, so use more classes, that’s my opinion.

Describe the z-index and how the stacking context is formed?

Z-index

All the character ‘z’ comes from the representation of three dimensions x, y, and z, in which x and y stand for width and height and the third dimension is z which stands for depth. So, CSS provides a property called the z-index that we can use to determine the depth of elements in our webpage.  The z-index property does not work with statically or non-defined positioned elements.

How stacking context is formed

<!DOCTYPE html>
<html>
<head>
<title>z-index</title>
<style type="text/css">
.box{
height: 150px;
width: 150px;
position: relative; }
.box-red{
background: red;
z-index: 1; }
.box-blue{
background: blue;
bottom: 80px;
left: 55px;
z-index: 2; }
.box-yellow{
background: yellow;
top: 25px;
left: 25px;
z-index: 3; }
</style>
</head>

<body>
<div class="box box-red">
<div class="box box-yellow"></div>
</div>
<div class="box box-blue"></div>

</body>
</html>

Output:

front interview question stacking context

1. All the default element position is static. To make it work, firstly you need to change the positioning behavior of boxes. You have to give a relative position to the box, z-index is 1 to the box red, z-index is2 to the box blue and z-index is 3 to the box red.

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2. See the output, the elements are all on the same level but still, one element comes in front of another one, it is known as the stacking context.

What are the pros and cons of CSS?

We know that CSS stands for cascading style sheet, it is used to create well-designed websites, because CSS is a presentational language. There are so many benefits of learning CSS or using CSS while web designing.

Pros of CSS

CSS allows us to add styles, animations, transitions, and various effects to web pages. It allows us to create consistent and easy-to-maintain websites. It allows us to easily implement design principles to websites. CSS allows us to separate the structure of a web page from a presentation of a webpage. It allows us to develop websites rapidly which stands for RAD(Rapid Application Development. It allows us to create well-designed websites.

Cons of CSS

CSS is used to add design aesthetics or design principles, styles, and effects to web pages. We can’t create more interactive dynamic and real-time websites using Just CSS and HTML. So creating real-time simulations, games, and web applications are not possible using just CSS and HTML. To overcome this limitation we use scripting languages like JavaScript, PHP, etc.

Note: We use scripting languages to create interactive, dynamic, and real-time websites or web applications like games, real-time simulations, etc. CSS has no capability of creating dynamic real-time websites.

Features of well-designed websites

Consistency

It is a consistent look and feels throughout the website lack of deviation. So, you need to maintain a consistent look and feel when you navigate from one web page to another page. You can implement consistency by using a consistent layout and creating, a consistent structure of web pages. consistent color usage, consistent fonts, consistent navigation mechanism, etc.

Readability

It is the ease with which the target audience can read and understand the content available on the website. So, the content that we place on web pages or web site should be easily understandable and readable by the target audience. You can implement readability using proper color schemes, variation in font sizes, variation in image sizes, and utilizing the space available in a proper way. These are some ways to implement readability.

Accessibility

It is the quality of content to which the target audience has access, accessibility means guiding the target audience’s eyes towards what you expect them to see. For ex: We need to make some research on the expectations of a target audience who visits our website, we need to understand their interests. Why do they visit our website, what do they want to get out of our website, and then all you need is to collect that content. And put it on the website, in such a manner that the target audience’s eyes should be moved directly toward that content that is accessible.

Maintainability

It is easy for developers and designers can update and manage websites. So, you should create a maintainable website at any time something needs to be modified developers can be able to modify that easily. For ex: what you need means you use proper code methodologies of course we are going to learn all the different coding methodologies.

You are going to implement consistency, readability, accessibility, and maintainability in a website. You are going to create your profile by using CSS and HTML.

List as many values for the display property that you can remember

The 4 most important values ​​used in display property are Inline, Block, Flex, and none. There is also a newer option of the display property called flex when we use it for building flexbox layout. Flex also provides an easier way for positioning elements in our layout. Every HTML element has a default display behavior. You can use this to change your HTML element anywhere. The reason why so many people use, this property is to convert block element to inline element and inline element to block element.

Block value

If an HTML tag displays its content on the new fresh line and occupies the complete available width of its parent tag, then such an HTML tag is called a block level tag.

Ex: <h1>-<h6>, <p.,<div>etc.

Inline value

If an HTML tag displays its content on the same line and occupies the exact amount of space required to display its content, then such an HTML tag is called an inline element. (I.e, it does not move content to a new fresh line and won’t take any extra space on the browser)

Ex:<strong>, <em>, <font>, <span>etc.

None Value

It is used to prevent HTML element output. If you use the “none” value in a display, the background will also hide and the content below will automatically upward. If you set this to the body tag, the body (entire page) will disappear or be hidden.

Ex: Display: none

Difference between CSS cascade vs CSS inheritance

Cascade

Inheritance

CSS inheritance deals with how styles are pulled down from the parent element to its child elements. Certain properties like font-family get inherited.

If you set a font family on the body element, it will be inherited by all elements in the body tag, meaning that if you set a default font face for a body tag, it will become the default font face of every HTML element. font.

If you said text color in the body tag, we know that every element’s text-color changes to that color, that is the default text color. So, the text color and font family are going to be inherited, whereas some properties will not get inherited to the child elements, like background color or height properties are not inherited.

What happens when we define a set of style rules for a specific tag in external, internal as well as inline styles?

When we define a set of style rules for a specific tag in external, internal as well as inline style, then the browser creates a virtual declaration list by merging all style rules by following “rules of cascade“, and then applies the merged virtual declaration list to specified tag in our HTML document.

The Rules of cascade

  1. Later properties override earlier properties which means the nearest properties to a tag are going to win.
  2. More specific selectors override less specific selectors which means less generic selectors override more generic selectors.

The highest precedence will be given to the second cascade rule than the first Cascade rule.

JavaScript Interview Questions

How can you declare a class in Javascript?

public class MyClass{
//field
//constructor
//method declaration
}

In the above code, Before the class declaration, we can add the modifier Public. The field declaration provides the state of the class and its object. Using the constructor, we can initialize the object. And methods to implement the behavior of the class and its objects. Between the opening parenthesis and the closing parenthesis, this part is called the class body.

Difference between null and undefined

This one’s a little bit of a tricky question because they both are falsy values in JavaScript.

Null vs undefined frontend interview quetion

Undefined

It is JavaScript Datatype, like boolean, string, etc. With undefined, the variable may or may not have been declared and it has not been given a value. Intentionally assigning a variable the value of undefined chances are you’re just going to run into reference errors because you’re trying to manipulate a variable that has not been defined yet or is out of scope. Undefined value in Javascript is used to define exactly what or name suggests.

Also, the value of undefined is always supposed to be assigned by the JS engine. The engine automatically assigns the undefined value for any variable that we forget to initialize. Although it can be explicitly assigned to variables it is considered to be a bad programming practice. Also, non-existing keys on an object when accessed give the result as undefined.

Null

It is a JavaScript object. Null represents the intentional absence of an object null is a value, that sometimes you will intentionally assign to a variable or return from a function. It denotes deliberate empty or a non-existent value instead of a non-initialized one. Which is quite similar to the concept of null in other languages like c++ and java. when an object in javascript is assigned the null value it means that the variable previously pointing to the object will now point to nothing. The value null is always assigned by the programmer whenever there is a need to assign empty values also some methods return null as a result when none of the expected results are found.

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To convince the interviewer, you need to say a few keywords that you know the concept at hand. For this entry level front-end developer interview questions
, when talking about undefined, make sure to say declared, uninitialized, engine assigned.

Explain AJAX in as much detail as possible?

Ajax stands for asynchronous JavaScript and XML is a way to use Javascript to talk to a web server get back a response and update a webpage. All without loading new web pages. This makes your website feel faster and more responsive. Ajax seemed like some kind of library does it work with PHP. Ajax is merely a web development technique used to send and retrieve data in the background without refreshing a web page.

Some examples of Ajax in action,

  1. When you first visit Google maps the entire page loads of the map a search map and a few navigation buttons. If you type a location into the search box. You don’t get a new web page you get a new map. And some of the user interface elements change but you’re still on the same web page. It’s the power of Ajax.
  2. Twitter is another website that takes advantage of ajax. If you use Twitter you may have noticed that as you scroll down to the bottom of the page older tweets appear it’s a page that never ends that all thanks to the power of Ajax loading more tweets whenever you scroll to the bottom of the page new content without loading new web pages.
  3. Ajax has lots of uses on the popular entertainment news and social networking site Reddit users can vote posts up and down helping to move the most popular posts to the top of the homepage. When clicking the up arrow on any post, without leaving the current web page but your vote is sent to the Reddit server using Ajax.

Explain higher order functions in JavaScript

It is one of those terms that sound intimidating and complicated but it’s simple. Essentially higher-order functions are a fancy term, we used to describe JavaScript functions that either take in or return other functions. So, you already know that you can pass in strings, numbers, objects into javascript functions and because a javascript function is also an object. It should come as no surprise to you that you can also pass in javascript function into other functions. We should have a counter to describe how many times I’m going to say the word function. .map() and .filter() are build in array methods that are extremely popular examples of higher-order functions.

For example: Loop through each element in an array and returns a new array. How do we tell the dot map what we want to do with each element as it’s looping through? This is why we need to pass a callback function into a dot map to tell the function. What do we want to do with every single element in the array as we’re through looping? A dot map takes in a function as a parameter is a higher-order function.

What are arrow functions and name a key difference between arrow functions and regular Javascript functions?

const array1=[1, 4, ,9, 16];
//pass a function to map
const mapq = array1.map((x) => {
return x * 2; });

console.log(map);
//expected output: Array [2,8,18,32]

 In arrow functions, we can get rid of the function keyword, but also if the function consists of only a return statement followed by a single line of code. We can remove the curly braces. And can also remove the return keyword because the arrow function will implicitly return. If the function only has one argument, we can even remove parentheses.

Difference between arrow functions and regular javascript functions,

const Car = (color)=> {
this.color = color; };
const redCar = new Car{'red');
//expected output: TypeError, Car is not a constructor

One key difference between regular functions and arrow functions is that you cannot use arrow functions as object constructors. So, you’ll see the example here, that it will throw a type error. By the way, there’s a lot more to arrow functions.

What will be logged in the console when the code is executed?

These types of entry level front-end developer interview questions
are super popular because they test your comprehension and understanding of the concepts rather than just memorizing a bunch of facts.

function run() {
console.log(1);
setTimeout(function(){console.log(2)}, 1000);
setTimeout(function(){console.log(3)}, 0);
console.log(4); }

We know that the JavaScript engine runs through the code line by line. In the above code, the first thing that’s going to be output is one, we also know that the last thing that’s going to be logged will be two. since there is a one-second delay that has none of the other lines. The third line has a set timeout of zero, so logically it should run immediately. This is kind of a trick entry level front-end developer interview questions and it requires an understanding of javascript events and timing.

So, really what’s happening is that the Javascript event loop only checks the event queue if the call stack is empty. The call stack takes presence only when all the functions have finished running does it check the even loop. When we call set timeout with zero milliseconds, what we’re saying is to call the callback function as soon as possible. When the function stack is empty, the next console latch will be four and after that, it will be number three.

What are javascript promises and name a use case?

If you have done any sort of web development, I’m sure you’ve run into asynchronous functions such as making an Ajax call or a set timeout.

Say you want to wait for that asynchronous to complete before you do something else, like loading a list of images that you made the Ajax call. Essentially, you want to wrap your asynchronous function inside a promise object. After calling your function asynchronous code, you can call back whatever you want to run inside the dot when that synchronous function completes.

What is the difference between GET and POST when making an Ajax request?

I feel like these entry level front-end developer interview questions
are asked at many web development companies. GET and POST is two different HTTP requests.

When retrieving data from a remote server, you want to use GET, for example, the Twitter API.

When you want to send data from the client to the server to create or update a server page, you want to use POST. For example, A user creates a new blog post in your web application. And we want to send that data to the server to store it, and if so, we want to use the post.

What does JSON stand for and what is it used for?

JSON stands for JavaScript Object Notation. It is essentially a text-based data format that makes it easy to share information across the web. For ex: If you’re sending data from the client to the server or requestion data from an API typically that comes in JSON format. The structure of JSON looks a lot like a JavaScript object literal but the two are not the same thing. The fact that they look a lot alike makes it easy to convert one to another and vice versa.

Structure of JSON:

"id" : "VIDEO_ID",
"latitude": "42.3464",
"longitude": "-72.0364",
"recordingdata" : "2013-10-30"

Difference Between “==” and ” ===” in JS?

Double equals (==)

Triple equals (===)

The double equals “==” will try to coerce the two values being compared into the same data type. A triple equals “===” will not do any sort of type of coercion.
Double equals not care about the data types. It does care about the data types.
It is a test for abstract equality It is a test for strict equality
Attempt to resolve data types through type coercion before comparison. Return false, if the types are different

Example:

console.log(1 == '1'); //true
console.log(1 === '1'); //false
console.log(false == 0); //true
console.log(false === 0); //false

Conclusion

I hope these entry level front-end developer interview questions are useful to you in some way. Differences and JavaScript are often asked in front-end interview questions.

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