Async functions✓Baseline · Widely available

async function loadUser(id) {
  try {
    const res = await fetch(`/api/users/${id}`);
    return await res.json();
  } catch (err) {
    console.error("Failed to load user", err);
  }
}

// Syntax can't be tested with an if-statement — an unsupported
// browser fails to parse the whole script. Either transpile for older
// targets (e.g. Babel/TypeScript/esbuild), or probe in isolation:
let supported = true;
try {
  new Function("/* code that uses the syntax */");
} catch {
  supported = false;
}