Front End Web Developer interview questions and answers

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Front End Web Developer Interview Questions

In some respects even the most technical role demands qualities common to strong candidates for all positions: the willingness to learn; qualified skills; passion for the job.

Even college performance, while it helps you to assess formal education, doesn’t give a complete picture. This is not to underplay the importance of a solid background in computer science. Some things to look for when hiring a web developer:

• Understanding of basic algorithmic concepts
• Discuss basic algorithms, how would they find/think/sort
• Can they show a wider understanding of databases
• Do they have an approach to modelling?

Do they stay up to date with the latest developments? If so, how? Probe for their favourite technical books. Who are they following on Twitter, which blogs do they turn to?

Are they active on Github? Do they contribute to any open source software projects? Or take part in Hackathons. In short, how strong is their intellectual interest in their chosen field? How is this demonstrated? Ask for side projects (like game development). Committed, inquisitive candidates will stand out.

Computer Science questions

Web

• Which HTTP status codes classes are used to designate success, client error and server error respectively?
• Describe event propagation (bubbling phase) in your own words. Is there any other phase in the DOM Event flow that you know of?
• When do DOMContentLoaded and Load events get fired ?
• Would you place an async script tag right before </body> ?
• Describe the same-origin policy as part of the web browser security model. Give a couple of practical limitations it may pose.
• Why is HTML5 History API so essential for all single page applications?
• What storage options do modern browsers provide ?
• Which steps constitute the Critical Rendering Path for web browsers?
• Why do you think PageVisibility API is useful?
• Give a basic overview of the Push web technologies available today

Javascript

• What Javascript engines do you know of?
• Are objects in Javascript passed by reference or by value?
• What does “1” + 2 + 4 evaluate to? What about “1” == 1 ?
• Write a code snippet demonstrating the usage of the ES6 Promise API
• Explain why the following doesn’t work as an IIFE:

  function foo(){ }();

• Explain Function.prototype.bind.
• Describe what a closure is in your own words.
• You have an idea you want to try out quickly enough. What tools would you use to prototype it?
• What is this event loop all about? A mouse click would result in a new item being added to the call stack or the task queue?
• What is alert going to show?

  var foo = 1;
  function bar() {
    if (!foo) {
      var foo = 10;
    }
    alert(foo);
  }
  bar();

 HTML/CSS

• Why would you use <strong> instead of <b> ?
• What are some of the key new features in HTML5?
• What’s doctype for?
• Is it generally a good idea to position CSS <link>s before <script> tags?
• Explain the CSS box model. Which properties are a part of it?
• Describe z-index and how stacking context is formed.
• How is responsive design different from adaptive design?
• What is the difference between classes and IDs in CSS?
• What’s the difference between display: inline and display: inline-block?
• What’s the difference between a relative, fixed, absolute and statically positioned element?