It depends on your existing skill level and the amount of time and effort you are willing to put into learning the language. For someone with a background in programming or a related field, it may take a few weeks or months to become proficient in JavaScript. For someone with no prior programming experience, it may take longer. The important thing is to have a good understanding of the fundamentals and to practice coding regularly. There are many resources available online such as tutorials, videos, and forums to help you learn and practice JavaScript, and it can also be helpful to work on projects or contribute to open-source projects to gain real-world experience. Ultimately, the time it takes to become proficient in JavaScript will vary depending on the individual and their learning style.
First read the answer fully, then try to explain it in your own words. After that, open a few related questions and compare the concepts. This method helps you remember the topic for a longer time and improves exam preparation.