javascript - How would I use an asynchronous function as a default parameter for another function -

i trying make function call function if parameter doesn't exist.

for example:

function getallfoo(){     // makes request api , returns array of foos }  function getnumfoo(foosarray = getallfoo(), num = 5){     // selects num of foos foosarray or calls getallfoos selects num of them } 

try wrap asynchronous function js promise, , in dependent function call then() function:

function getallfoo () {   return new promise(     // resolver function called ability resolve or     // reject promise     function(resolve, reject) {       // resolve or reject here, according logic       var foosarray = ['your', 'array'];       resolve(foosarray);     }   ) };  function getnumfoo(num = 5){   getallfoo().then(function (foosarray) {     // selects num of foos foosarray or calls getallfoos selects num of them   }); }