Top 20 Front End Developer Interview Questions and Answers

Question

1. What technologies are required for Front End Developers?

Answer 1

Front End Developers or Web Developers must know the below technologies to work on the Front End side of applications.

Answer 2

When you want to pass a function inside another function as an argument to complete some task, it is known as a Callback function. This callback function is invoked inside an outer or calling function to perform some kind of action.


    function greet(name) {
    alert('Hi ' + name);
    }

    function processInput(callback) {
    var name = prompt('Please enter your name.');
    callback(name);
    }

    processInput(greet);

This is an example of synchronous callback function. Next question is an example of asynchronous callback functions.

Answer 3

When you work with asynchronous programming in JavaScript, eventual completion or failure of that operation is represented as a Promise. Promise provides certain benefits as below.

Promise allows you to add callbacks using then(), It ensures that callbacks will never be invoked before current run completion of JavaScript event loop.
If you add the callbacks after the success or failure of operation that promise represents then callbacks will be invoked in any case.
If you want to add multiple callbacks, you can use then() function several times. All callbacks will be invoked in the same order in which they were applied.
When you want to perform multiple asynchronous operations one after another, you can use Promise chaining. Promise Chaining allows you to combine multiple asynchronous operations where subsequent operations use the result from the preceding operation.

For more you can visit Promises in JavaScript.

Answer 4

var and let both allow you to declare variables in different ways in JavaScript. let allows you to declare some variable at block-scoped level, or expressions on which it used Whereas var allows you to declare a variable globally or locally to function rather than to a block scope. Another difference between var and let is that let variable is initialized to a value only when code executes it or parser evaluates it and var declarations are processed whenever they occur, before any parser evaluates these (It's known as hoisting). Let's understand from Example.


    function varTest() {
    var x = 4;
    {
    var x = 5;  // same variable!
    console.log(x);  // 5
    }
    console.log(x);  // 5
    }

    function letTest() {
    let x = 4;
    {
    let x = 5;  // different variable
    console.log(x);  // 5
    }
    console.log(x);  // 4
    }

For more visit let vs var.

Answer 5

Redux is an open-source JavaScript library which is a predictable state container for JavaScript Applications. It comes with the following characteristics.

Answer 6

Yes, we can design any logo using HTML and CSS.

Answer 7


    <div id="google"></div>
    // css to print Google Circle with all the colors.
        #google {
        position: relative;
        border-top: 100px solid #EA4335;
        border-right: 100px solid #4285F4;
        border-bottom: 100px solid #34A853;
        border-left: 100px solid #FBBC05;
        border-radius: 50%;
        background-color: #FFFFFF;
        width: 300px;
        height: 300px;
        padding: 0;
        margin: 10vh auto 0;
        }
    
    // below css will convert that circle to 'G' logo of Google.
        #google::before {
        content: "";
        z-index: 100;
        position: absolute;
        top: 50%;
        right: -95px;
        transform: translateY(-50%);
        width: 245px;
        height: 100px;
        background: #4285F4;
        }

        #google::after {
        content: "";
        z-index: 101;
        position: absolute;
        border-top: 200px solid transparent;
        border-right: 200px solid #FFFFFF;
        top: -100px;
        right: -100px;
        width: 0;
        height: 0;
    }

Answer 8

For more visit Local Storage and Session Storage.

Answer 9

For more visit Secure a Cookie.

Answer 10

When you attend an interview, Interviewer may ask you to rate yourself in a specific Technology like Front End, So It's depend on your knowledge and work experience in Front End.

Answer 11

This question may be specific to your technology and completely depends on your past work experience. So you need to just explain the challenges you faced related to Front End in your Project.

Answer 12

It's based on your role and responsibilities assigned to you and what functionality you implemented using Front End in your project. This question is generally asked in every interview.

Answer 13

Here you can tell about your overall work experience on Front End.

Answer 14

It depends on the candidate whether you have done any Front End training or certification. Certifications or training are not essential but good to have.

Answer 15

We have covered some frequently asked Front End Interview Questions and Answers to help you for your Interview. All these Essential Front End Interview Questions are targeted for mid level of experienced Professionals and freshers.
While attending any Front End Interview if you face any difficulty to answer any question please write to us at info@qfles.com. Our IT Expert team will find the best answer and will update on the portal. In case we find any new Front End questions, we will update the same here.

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Top 20 Front End Developer Interview Questions and Answers

Front End Interview Questions and Answers

Some General Interview Questions for Front End

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