ECMAScript Standards

Short explanation

ECMAScript is the standardized specification of JavaScript maintained by TC39, a committee that reviews proposals and evolves the language. Standardization ensures that different engines implement the same language features.

Real-world example

Modern JS features like async/await and Promise were standardized through a proposal process. Consider async/await which simplified writing asynchronous code that previously required complex Promise chains or generators.

// Before async/await (Promises)
fetch(url)
  .then(res => res.json())
  .then(data => console.log(data))
  .catch(err => console.error(err));

// With async/await
async function load() {
  try {
    const res = await fetch(url);
    const data = await res.json();
    console.log(data);
  } catch (err) {
    console.error(err);
  }
}

How JS handles it internally

When a proposal becomes part of the standard, engine authors implement it in their runtime (parsers and compilers). Some features require bytecode or JIT engine changes (for example, optimizations for tail calls or new opcodes), and engines provide polyfills for older environments when possible.

Diagram

Related

🔗 Related:

• Birth of JavaScript
• Modern JavaScript Era

FAQ

Q: What is TC39?

A: TC39 is the technical committee under ECMA International that shepherds JavaScript's language evolution through a proposal process.

Q: Can I use stage-x proposals today?

A: Some proposals are available via transpilers and polyfills, but using them in production requires caution due to potential API changes.