FileList.forEach

We can't use forEach on FileList data structure. FileList is an object, not an array. To convert it to array, we have to use Object.values, or use spread operator:

function handleFiles(files) {
    console.log(files);
    alert(Array.isArray(files)); // false
    alert(Array.isArray(Object.values(files))); // true
    alert(Array.isArray([...files])); // true

    // this won't work:
    //      files.forEach(uploadFile);

    [...files].forEach(uploadFile);
}

function uploadFile(file) {
    alert('uploading ' + file.name);
}