Seek into local files with the File System API

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If you have a File object (say, one stored using the FileSystem API), it's possible to seek into it and read chunks without reading the entire file into memory:

var url = "filesystem:";

window.webkitResolveLocalFileSystemURL(url, function(fileEntry) {
fileEntry.file(function(file) {
var reader = new FileReader();

reader.onload = function(e) {
var ab =; // arrayBuffer containing bytes 0-10 of file.
var uInt8Arr = new Uint8Array(ab);

var blob = file.webkitSlice(0, 10, "application/zip"); // mimetype is optional
}, errorHandler);
}, errorHandler);

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