Please, can someone help me : I have problem with async function, I will save all object of async function in table pages, but in result I get empty table?

var pages=[];                                                    

function pdftoimg(url){
    var promise=new Promise(function (resolve,reject){
        pdfjsLib.getDocument(url).then((pdf)=>{
            length_files=pdf.numPages;
            for(var i=1;i<=length_files;i++){
                pdf.getPage(i).then((page)=>{
                    pages.push({pagenumber:i,pagedata:page});
                });
            }
            resolve();
        });
    });
    return promise;
}

console.log(pages)// get empty table []