{"id":5338,"date":"2026-09-29T01:00:31","date_gmt":"2026-09-29T04:00:31","guid":{"rendered":"https:\/\/nextage.com.br\/blog\/?p=5338"},"modified":"2026-09-28T17:08:04","modified_gmt":"2026-09-28T20:08:04","slug":"10-things-every-javascript-developer-should-know-in-2027","status":"publish","type":"post","link":"https:\/\/nextage.com.br\/blog\/en\/10-things-every-javascript-developer-should-know-in-2027\/","title":{"rendered":"10 Things Every JavaScript Developer Should Know in 2027"},"content":{"rendered":"
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JavaScript remains the foundation of modern software development. The Stack Overflow Developer Survey 2025<\/a> gathered more than 49,000 responses from 177 countries, and JavaScript came out as the most used language, at 66%, ahead of HTML\/CSS (62%) and SQL (59%). This leadership is nothing new: according to the Stack Overflow blog<\/a>, JavaScript has ranked first every year since the survey began in 2011.<\/p>\n

What changes from one year to the next is what the market expects from people who work with the language. TypeScript has become the standard for new projects, AI tools now write part of the code, the language has gained a new date and time API, and attacks on the npm dependency supply chain have become a real security concern for companies. Even so, fundamentals are still what separate average professionals from truly productive ones.<\/p>\n

Below is what every JavaScript developer should know heading into 2027, both for those who write code and for those who lead or hire technology teams.<\/p>\n

Summary: 10 things every JavaScript developer should know<\/strong><\/p>\n

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  1. How JavaScript runs code: call stack, event loop and asynchronous programming<\/li>\n
  2. Scope, hoisting, closures and how this works<\/li>\n
  3. Types, coercion and why TypeScript became the standard<\/li>\n
  4. Modern JavaScript, from ES2015 to the Temporal API<\/li>\n
  5. Runtimes and modules: Node.js, Bun, Deno, ESM and CommonJS<\/li>\n
  6. Frameworks: fundamentals before tools<\/li>\n
  7. Tooling and quality: build, linting, testing and CI<\/li>\n
  8. Web performance and Core Web Vitals<\/li>\n
  9. Application security and the npm supply chain<\/li>\n
  10. AI-assisted development, with critical thinking<\/li>\n<\/ol>\n

    \"Developer<\/p>\n

    10 things every JavaScript developer should know<\/strong><\/h2>\n

    1. How JavaScript runs code: call stack, event loop and asynchronous programming<\/h3>\n

    The event loop is the mechanism that allows JavaScript, which runs one task at a time on a single thread, to handle asynchronous operations without freezing the application. It coordinates the call stack, the microtask queue (Promises) and the task queue (timers, events).<\/p>\n

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    <\/div>\n<\/div>\n
    javascript<\/div>\n
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    console.log('1');\r\nsetTimeout(() => console.log('2'), 0);\r\nPromise.resolve().then(() => console.log('3'));\r\nconsole.log('4');\r\n\/\/ Output: 1, 4, 3, 2<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n
    The result surprises anyone unfamiliar with the model: microtasks (Promises) always run before tasks scheduled with setTimeout, even with a zero delay.<\/p>\n
    Why it matters:<\/strong> many hard-to-reproduce production bugs (race conditions, frozen screens, out-of-order requests) come from an incomplete understanding of asynchronous code. Mastering Promises and async\/await, including error handling with try\/catch and Promise.all for parallel calls, is a basic requirement. MDN’s documentation on the event loop<\/a> is the best starting point.<\/p>\n
    2. Scope, hoisting, closures and how this works<\/h3>\n
    A closure is a function’s ability to remember the variables from the scope in which it was created, even after that scope has finished running. It is one of the concepts most often covered in technical interviews, and for good reason: it powers React hooks, middleware and much of the ecosystem’s libraries.<\/p>\n
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    <\/div>\n<\/div>\n
    javascript<\/div>\n
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    function createCounter() {\r\n  let total = 0; \/\/ private variable, not accessible from outside\r\n  return () => ++total;\r\n}\r\n\r\nconst count = createCounter();\r\ncount(); \/\/ 1\r\ncount(); \/\/ 2<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n
    Three points complete this knowledge:<\/p>\n