index.js

const arr = ["jose", "juan", "pedro", "diego" ]
function timeout(ms) {
    return new Promise(resolve => setTimeout(resolve(console.log('during loop...')), ms));
}

function processing(arr) {
 let mapped =   arr.map(name =>  name.toUpperCase())  
 timeout(4000) 
 let filtered =  mapped.filter(name =>  name.startsWith("J") )
 return filtered; 
}

console.log(processing(arr))
  //.then(result => console.log(result) )