Overloading the await keyword.

await is a keyword in js that works in async code blocks to wait for a promise to resolve. While it is a keyword, it is not reserved. This means it can be overloaded at the global level. When you do this, you can get some interesting behavior. Consider this example.

<script>
globalThis.await=_=>_;
console.alog = async(x)=>{
  await "wtf";
  console.log(x);
};
</script>

<script>
await(console.alog(1));
console.log(2);
// prints 2 then 1
</script>

<script type="module">
await(console.alog(1));
console.log(2);
// prints 1 then 2
</script>

What's happening is we are assigning a property await to the global object that just takes a parameter and returns it. So now when you call await(x); in synchronous code, you get the new behavior but when you call await(x); in async code you get the original behavior. Regular script tags run synchronously at the top level so there is no waiting. In modules, the top level runs asynchronously so the result is awaited as you might expect.