Why this matters:

WebSockets and server-sent events are two different technologies that define how browsers and clients communicate with each other. While neither is explicitly better than the other, a strong JavaScript developer will have a good understanding of both and be able to discuss the differences and similarities.

What to listen for:

  • Candidates should be able to clearly and concisely describe what the two technologies are and when they’re appropriate to use.
  • Candidates may also mention technologies like long-polling and short-polling, which is a sign they have a strong knowledge base.

Why this matters:

Ajax, which stands for asynchronous JavaScript and XML, is a set of web development tools that enable developers to change parts of a web page in the background without reloading the entire page. Candidates should have a thorough understanding of the role Ajax has in streamlining the server communication process for web applications.

What to listen for:

  • Listen for references to improved interactivity and maintaining Javascript variables and DOM state on a page.
  • Strong answers may mention disadvantages, including the difficulty of bookmarking dynamic pages.

Why this matters:

JavaScript templating is a simple and useful strategy used to separate HTML structures from the JavaScript strings they contain. Strong candidates will be able to discuss the benefits of templating in speeding up front-end development, and making debugging and maintenance simpler and faster.

What to listen for:

  • Answers may include libraries like Mustache.js and Handlebars.js.
  • Listen for the candidate’s reasoning on which templating engines are best depending on performance-critical projects and other variables.

Why this matters:

User experience (UX) should be of utmost importance to a JavaScript developer. It’s essential that they have the end user in mind when developing a new website or web application. What best practices do they follow for their projects? Have they tested assistive solutions to ensure the website or application is accessible to all potential users?

What to listen for:

  • Strong candidates will have firsthand experience implementing usability and accessibility standards.
  • Top answers may mention performing user testing across various devices, ensuring the site or app worked seamlessly and intuitively no matter how a user engaged with it.

Why this matters:

JavaScript developers must collaborate with other stakeholders, either on the company or the client side, to create an end product that meets their requirements. They should be flexible but also committed to their own vision in order to make a case for development decisions they believe in.

What to listen for:

  • Look for signs the candidate was able to listen to the feedback and gracefully navigate the pushback.
  • Great candidates may have been able to propose a compromise or persuade a stakeholder to try it their way.

Why this matters:

Since JavaScript developers often collaborate with many team members to move a project through to completion, your candidate’s approach to working with others is essential. Your candidate should display signs that they were a source of motivation and also committed to understanding the design and functionality requirements.

What to listen for:

  • Strong answers will convey the importance of having many viewpoints to reach a better end product.
  • Great answers will show that the candidate asked insightful, detailed questions along the way to get more information.

Why this matters:

When it comes to browsers, user preferences must be considered in order to provide a uniform exceptional experience regardless of how people choose to access your website. Browser compatibility can be difficult to troubleshoot, so the candidate’s answer can demonstrate whether they have patience.

What to listen for:

  • Candidates should show they’re dedicated to working through the issues, no matter how often they come up.
  • A good response will demonstrate attention to detail and a passion for delivering the best possible user experience.

Why this matters:

The best JavaScript developers have ambition and their willingness to learn. To keep up with the rapidly evolving development landscape, candidates should have eagerness to stay ahead of the curve. Why do they want to master this technology? How will they go about doing it? Do they believe it will help them provide more value to the company?

What to listen for:

  • Strong answers might mention taking a boot camp in their spare time or following forums and blogs that center around the technology.
  • Ideally, they will already be taking steps to learn the technology.

Why this matters:

Stack Overflow is a popular resource for JavaScript developers, where questions are asked and answered by the wider tech community. The candidate’s answer will show whether they’re in tune with the industry and have passion for their field. If they haven’t heard of Stack Overflow, it may be a red flag that they’re not the right fit.

What to listen for:

  • Look for indications that the candidate is engaged in the community at large.
  • Strong candidates may mention specific questions they asked or answers they provided, showing a willingness to help others.