Definitely not, though you will be asked about any syntax errors you make—interviewers don’t necessarily mind the errors themselves that much, but they do want to see how you correct them (and how you react when those errors are pointed out to you). Interviewers also care about whether or not you can develop and explain an algorithm on a whiteboard before actually writing any code. Only then, when you and the interviewer have talked through the logic of the algorithm, should you actually dive into coding.
This often surprises programmers about their interviews, not because they have to use a whiteboard before writing any code, but because communicating their thinking is harder than they expect. This normally happens because programmers ignore the non-technical skills when preparing for their coding interviews, an oversight that can cost them the job. It’s important that you prepare for every aspect of the interview, and make use of the resources that match the skills you need to work on most.
If you’re confident in your coding skills and would like to focus on the behavioral side of your interviews, Interviewing.io is a great place to look. You’ll get matched in technical mock interviews with other software engineers—some of whom have worked at companies like Google and Facebook—and receive immediate, unbiased feedback on your performance.
If you think you’d benefit more from a deeper knowledge of data structures, algorithms, and systems design, you may want to enroll in a course like Tech Interview Pro, which was designed by a former Google software engineer. TIP is laser-focused on helping you ace your big tech interviews, and includes 150+ in-depth video lessons on data structures & algorithms, systems design, and the interview process as a whole. Students get access to a private Facebook group of 1,500 former students, many of whom have applied what they learned in the course to land jobs at Facebook, Google, Amazon, and other big tech firms.
And while one or two errors won’t annihilate your chances of success (refer back to what I said at the beginning), your coding skills should still be as sharp as possible. To hone them, you can turn to sites like LeetCode, a very popular online judge with thousands of coding problems to solve, or CodeKata, another problem library focused on bridging the gap between algorithm theory and real-world application.
Good luck with the interview.