JSFiddle - React, Tailwind, and code Playground

JavaScript

function mainFunc(){  
  var test = promiseFunc().then(function(result){
    return result;
  })
  alert(test); // should be true value
  return test;
}

function promiseFunc(){
  return new Promise(function(resolve, reject){
  	alert(1);
    resolve(true);
  })
}

mainFunc();