Esta pregunta se ha hecho antes, pero todavía no entiendo Establecer el valor de la variable en el bloque if. Valor de acceso fuera del bloque if En mi caso, eliminé una variable fuera del bloque if var title, artist, album, year pero cuando accedí fuera del bloque if filedata.push({fileName: file.name, location: path, title: title, artist: artist, album: album, year: year}) dice indefinido

 function selectMusic() { const fileList = songs.files for (let i=0; i < fileList.length; i++) { let file = fileList.item(i) var path = (window.URL || window.webkitURL).createObjectURL(file) var reader = new FileReader(); var title, artist, album, year reader.onload = function(e) { var dv = new jDataView(this.result); // "TAG" starts at byte -128 from EOF. if (dv.getString(3, dv.byteLength - 128) == 'TAG') { title = dv.getString(30, dv.tell()); artist = dv.getString(30, dv.tell()); album = dv.getString(30, dv.tell()); year = dv.getString(4, dv.tell()); } else { console.log('id3 metadata not found') } }; reader.readAsArrayBuffer(file); filedata.push({fileName: file.name, location: path, title: title, artist: artist, album: album, year: year}) //console.log(file.name) console.log(filedata) } //const arr = Array.from(fileList) // Load song initially loadSong(filedata[songIndex]); }