Using await outside of an async function

Question

I was attempting to chain two async functions together  because the first had a conditional return parameter that caused the second to either run  or exit the module  However  I ve found odd behavior I can t find in the specs   async function isInLobby           promise all  chained methods here       let exit   false      if  someCondition  exit   true      This is a bastardized snippet of my code  you can see the full scope here   that simply checks if a player if already in a lobby  but that s irrelevant   Next we have this async function   async function countPlayer         const keyLength   await scardAsync game       return keyLength      This function doesn t need to run if exit     true   I tried to do  const inLobby   await isInLobby      This I hoped would await to results  so I can use inLobby to conditionally run countPlayer  however I received a typeerror with no specific details   Why can t you await an async function outside of the scope of the function  I know it s a sugar promise  so it must be chained to then but why is it that in countPlayer I can await another promise  but outside  I can t await isInLobby

User · Answer

There is always this of course    async      gt        await             all of the script                nothing else   This makes a quick function with async where you can use await  It saves you the need to make an async function which is great    credits Silve2611

User · Answer

Top level await is not supported  There are a few discussions by the standards committee on why this is  such as this Github issue   There s also a thinkpiece on Github about why top level await is a bad idea  Specifically he suggests that if you have code like this      data js const data   await fetch    data json     export default data    Now any file that imports data js won t execute until the fetch completes  so all of your module loading is now blocked  This makes it very difficult to reason about app module order  since we re used to top level Javascript executing synchronously and predictably  If this were allowed  knowing when a function gets defined becomes tricky   My perspective is that it s bad practice for your module to have side effects simply by loading it  That means any consumer of your module will get side effects simply by requiring your module  This badly limits where your module can be used  A top level await probably means you re reading from some API or calling to some service at load time  Instead you should just export async functions that consumers can use at their own pace

User · Answer

As of Node js 14 3 0 the top-level await is supported   Required flag  --experimental-top-level-await   Further details  https   v8 dev features top-level-await

User · Answer

you can do top level await since typescript 3 8 https   www typescriptlang org docs handbook release-notes typescript-3-8 html -top-level-await From the post  This is because previously in JavaScript  along with most other languages with a similar feature   await was only allowed within the body of an async function  However  with top-level await  we can use await at the top level of a module   const response   await fetch         const greeting   await response text    console log greeting       Make sure we re a module export       Note there   s a subtlety  top-level await only works at the top level of a module  and files are only considered modules when TypeScript finds an import or an export  In some basic cases  you might need to write out export    as some boilerplate to make sure of this   Top level await may not work in all environments where you might expect at this point  Currently  you can only use top level await when the target compiler option is es2017 or above  and module is esnext or system  Support within several environments and bundlers may be limited or may require enabling experimental support

[javascript] Using await outside of an async function

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