I have a local program which writes a JSON object to a file so that a JavaScript can pick up its data and process it. The file is selected using an <input> object:
<form id = "getfiles">
<input type = "file" multiple id = "files" />
</form>
with the following JS function setInterval to repeat every 300ms. However, when the file changes, only Google Chrome reloads the file and processes the new content; I have to manually reselect the file on the page in IE 10 and Firefox 20.
function speakText()
{
var thefile = document.getElementById('files').files[0];
var lastChanged = thefile.lastModifiedDate;
var reader = new FileReader();
reader.onload = function(event)
{
var lcd = document.getElementById("last_change_date");
if (!lcd)
{
var spanLastChanged = document.createElement("span");
spanLastChanged.id = "last_change_date";
spanLastChanged.innerText = lastChanged;
console.log(lastChanged);
document.body.appendChild(spanLastChanged);
}
else
{
// compare lastChanged with last_change_date
var last_known_change = Date.parse(lcd.innerText);
// var last_known_change = Date.parse(thefile.lastModifiedDate);
if (last_known_change !== Date.parse(lastChanged))
{
console.log("Something is new since " + lcd.innerText);
var fileContent = event.target.result;
var commands = JSON.parse(fileContent);
handleJSON(fileContent);
lcd.innerText = lastChanged;
}
}
}
reader.readAsText(thefile, "UTF-8");
}
Firefox and IE are doing the right thing per spec: the File objects associated with a file input are supposed to be immutable snapshots of a file at the point when the File object was created. It's a known bug in WebKit/Blink that they just store a reference to the file's data, so that mutating the data will change what the File object sees.
In fact, the WebKit/Blink behavior is a privacy bug: when a user selects a file in a file input, they are giving a web page permission to read the data of the file at that time, not for all future versions of the file! Which is why the spec is written as it is.
Related
I'm trying to create a web application that can be used via a file:// URI. This means that I can't use AJAX to load binary files (without turning off security features in the browser, which I don't want to do as a matter of principle).
The application uses a SQLite database. I want to provide the database to a sql.js constructor, which requires it in Uint8Array format.
Since I can't use AJAX to load the database file, I could instead load it with <input type="file"> and FileReader.prototype.readAsArrayBuffer and convert the ArrayBuffer to a Uint8Array. And that's working with the following code:
input.addEventListener('change', function (changeEvent) {
var file = changeEvent.currentTarget.files[0];
var reader = new FileReader();
reader.addEventListener('load', function (loadEvent) {
var buffer = loadEvent.target.result;
var uint8Array = new Uint8Array(buffer);
var db = new sql.Database(uint8Array);
});
reader.readAsArrayBuffer(file);
});
However, <input type="file"> requires user interaction, which is tedious.
I thought I might be able to work around the no-AJAX limitation by using a build tool to convert my database file to a JavaScript object / string and generate a ".js" file providing the file contents, and then convert the file contents to a Uint8Array, somehow.
Psuedocode:
// In Node.js:
var fs = require('fs');
var sqliteDb = fs.readFileSync('path/to/sqlite.db');
var string = convertBufferToJsStringSomehow(sqliteDb);
fs.writeFileSync('build/db.js', 'var dbString = "' + string + '";');
// In the browser (assume "build/db.js" has been loaded via a <script> tag):
var uint8Array = convertStringToUint8ArraySomehow(dbString);
var db = new sql.Database(uint8Array);
In Node.js, I've tried the following:
var TextEncoder = require('text-encoding').TextEncoder;
var TextDecoder = require('text-encoding').TextEncoder;
var sql = require('sql.js');
var string = new TextDecoder('utf-8').decode(fs.readFileSync('path/to/sqlite.db'));
// At this point, I would write `string` to a ".js" file, but for
// the sake of determining if converting back to a Uint8Array
// would work, I'll continue in Node.js...
var uint8array = new TextEncoder().encode(string);
var db = new sql.Database(uint8array);
db.exec('SELECT * FROM tablename');
But when I do that, I get the error "Error: database disk image is malformed".
What am I doing wrong? Is this even possible? The database disk image isn't "malformed" when I load the same file via FileReader.
Using the following code, I was able to transfer the database file's contents to the browser:
// In Node.js:
var fs = require('fs');
var base64 = fs.readFileSync('path/to/sqlite.db', 'base64');
fs.writeFileSync('build/db.js', 'var dbString = "' + base64 + '";');
// In the browser (assume "build/db.js" has been loaded via a <script> tag):
function base64ToUint8Array (string) {
var raw = atob(string);
var rawLength = raw.length;
var array = new Uint8Array(new ArrayBuffer(rawLength));
for (var i = 0; i < rawLength; i += 1) {
array[i] = raw.charCodeAt(i);
}
return array;
}
var db = new sql.Database(base64ToUint8Array(dbString));
console.log(db.exec('SELECT * FROM tablename'));
And that's working with the following code:
input.addEventListener('change', function (changeEvent) {
var file = changeEvent.currentTarget.files[0];
var reader = new FileReader();
reader.addEventListener('load', function (loadEvent) {
var buffer = loadEvent.target.result;
var uint8Array = new Uint8Array(buffer);
var db = new sql.Database(uint8Array);
});
reader.readAsArrayBuffer(file);
});
However, <input type="file"> requires user interaction, which is
tedious.
Using current working approach would be less tedious than attempting to create workarounds. If user intends to use application, user can select file from their filesystem to run application.
I am very new to coding and javascript; just a few days in. I was wondering if there was a way to import objects from a text file(separated by lines) to use in my array: replyText. Here is what I'm working with:
// Variables
var theButton = document.getElementById("theButton");
var mainText = document.getElementById("mainText");
var replyText = [...,...,...,...,];
var i = 0;
// Functions
function nextText() {
mainText.innerHTML = replyText[i++ % replyText.length];
}
// MAIN SCRIPT
theButton.onclick = function() {
nextText();
};
You can use XMLHttpRequest to get the .txt file just pass the path of it.
var file = new XMLHttpRequest();
file.open("GET", "file:/../file.txt", false);
file.onreadystatechange = function () {
if (file.readyState === 4) {
if (file.status === 200 || file.status == 0) {
var text = file.responseText;
alert(text);
}
}
}
EDIT: you must pass the absolute path file:///C:/your/path/to/file.txt
For client/browser-side file reading:
You cannot easily read a file on the client-side as you are not allowed direct access to the client's file system. However, you can place a input element of file type in your HTML markup via which the client can load a file for your program to process. For example:
<input type="file" id="file" onchange="readFile()" />
Now when the client selects a file for use, the readFile() function will be called which will read and process the file. Here's an example:
function readFile() {
var file = document.getElementById('file').files[0]; // select the input element from the DOM
var fileReader = new FileReader(); // initialize a new File Reader object
fileReader.onload(function() { // call this function when file is loaded
console.log(this.result); // <--- You can access the file data from this variable
// Do necessary processing on the file
});
fileReader.readAsText(file); // Read the file as text
}
For more information on File Reader, check out the docs.
To add on to Paulo's solution, read below for splitting string by line breaks (new line character)
var replyText = text.split("\n"); // "\n" is new line character
I'm building a service for users where I must have private files.
Actually, with Cloud Code, I can control the download flux, through a function. But, how I can prevent a hacker to use the javascript console and upload his files ? He will get a link, which he can share with anyone without restriction and at my charges.
const file = Parse.File('hackerFile', hackerFileArray);
file.save().then(() => console.log(file.url)) // Now, he have a free file hosting.
Is there a way to completely remove this feature for everyone, except the master key ?
Example of hosting a file on http://todolist.parseapp.com/
Open the console in your browser then
var script = document.createElement('script');
script.src = '//www.parsecdn.com/js/parse-1.6.14.min.js'; // Because of their version.
document.head.appendChild(script);
Parse.initialize("0Oq3tTp9JMvd72LOrGN25PiEq9XgVHCxo57MQbpT", "vUFy2o7nFx3eeKVlZneYMPI2MBoxT5LhWNoIWPja"); // Found in their sources
var reader = new FileReader();
var input = document.createElement('input');
input.type = 'file';
document.body.appendChild(input);
// Then choose a file from the browser. I choosen a picture.
reader.onloadend = function() {
var file = new Parse.File('hackFile', {base64: reader.result});
file.save().then(function() {
console.log(file.url());
})
};
reader.readAsDataURL(input.files[0]);
Then you have a link. I got http://files.parsetfss.com/ae2ddbce-9cc0-4e1a-a16d-52ec5fdb7570/tfss-8fccfba0-ccf7-41cd-8f42-75f0a3478262-hackFile
Haven't tried this, but think it could work:
1) Add a beforeSave function on whatever class you're looking to prevent this behavior on.
2) In the beforeSave, check request.object.dirtyKeys() and iterate through each of those keys on the newly created object.
3) If the value associated with one of those dirtyKeys is a file, don't allow the file to save: response.error
Parse.Cloud.beforeSave(Parse.User, function(request, response) {
var dirtyKeys = request.object.dirtyKeys();
for (var i = 0; i < dirtyKeys.length; ++i) {
var dirtyKey = dirtyKeys[i];
if (isUnwantedFile(request.object, dirtyKey)) {
response.error("User is not allowed to store files");
return;
}
}
response.success();
});
//note this function is untested -- I'm not sure what type a user-created file would be,
//but basically if you can figure that out, substitute it in here
function isUnwantedFile(obj, key){
return typeof obj[dirtyKey] === Parse.File
}
I've been trying to save a user-uploaded image to parse for the longest time, and nothing seems to work -- even when following their documentation.
Below is the handler I use for the onChange() on a multiple file upload. At first I was concerned about multiple file uploads, but at this point just saving one image doesn't work.
function fileHandler(event) {
var files = event.target.files;
stopPictures = [];
$("#stop-img-container").empty();
if (files[0] != null) {
$("#stop-img-container").show();
for (var i = 0; i < files.length; i++) {
var file = files[i];
var picReader = new FileReader();
picReader.addEventListener("load",function(event){
var picFile = event.target;
var image = $("<img/>",{
"title": picFile.name,
"class": "stop-image",
"src": picFile.result
}).appendTo("#stop-img-container");
var name = picFile.name;
var dataFile = picFile.result;
var base64str = dataFile.substring(dataFile.indexOf("base64,")+7,dataFile.length);
var parseFile = new Parse.File(name,{base64:base64str}); // saving logs 404 Not Found from POST to "http://api.parse.com/1/files"
var parseFile = new Parse.File(name,dataFile); // saving logs "Uncaught Creating a Parse.File from a String is not yet supported."
var parseFile = new Parse.File(name,file); // saving logs 404 Not Found from POST to "http://api.parse.com/1/files"
var parseFile = new Parse.File(name,base64str); // saving logs "Uncaught Creating a Parse.File from a String is not yet supported."
parseFile.save().then(function (savedFile) {
stopPictures.push(savedFile);
alert("worked");
});
});
picReader.readAsDataURL(file);
}
} else {
$("#stop-img-container").hide();
}
}
There's some extraneous stuff here, but basically it collects the user's selected files, displays them for them once they've finished loading, and then creates them as a Parse file. I've left it in to show that at least something is working as it properly locally stores and previews the user's selected files.
I have included three different ways of creating the same Parse file. However, all of them fail when I try to save to Parse in any way.
Parse's Javascript API docs says that any of these should work fine. But they lie, or I'm an idiot.
Anyone have any idea why this doesn't seem to work? Seems like a pretty critical aspect of their API is broken completely -- which I find hard to imagine.
EDIT: I'm also positive I'm properly parsing (lower case p) the base64 string as this site confirms the appropriate image and works.
I experienced the same problem.
Finally I found what causes the problem.
It's a "file name".
I suspect the file name in tuckerchapin's example is null.
var name = picFile.name;
I wrote the example with React.
this code works fine.
class ImageUpload extends React.Component {
onChange(e) {
var file = e.target.files[0];
var parseFile = new Parse.File(file.name, file);
Parse.User.current().set("icon",parseFile);
Parse.User.current().save();
}
handleSubmit(e) {
e.preventDefault();
}
render() {
return (
<form onSubmit={this.handleSubmit}>
<input type="file" onChange={this.onChange.bind(this)} />
</form>
);
}
}
I'm using openxml in my HTML5 mobile app to generate word documents on the mobile device.
In general openxml works fine and straight forward, but I'm struggling with an annyoing problem.
The document generation only works the first time after I've started the app. This time I can open and view the document. Restart the app means:
- Redeploy from development machine
- Removing the app from the task pane (pushing aside; I assume the app is removed then?)
The second time I get the message the document is corrupted and I'm unable to view the file
UPDATE:
I can't reproduce this behaviour when I'm running the app connected to the remote debugger without having a breakpoint set. Doing it this way I always get a working document.
I doesn't make a difference wether I do any changes on the document or not. Simply open and saving reproduce this error.
After doing some research I've found that structure of the docx.zip file of the working and the corrupt file is the same. They also have the same file length. But in the corrupt docx there are some files I've found some files having a wrong/invalid CRC. See here an example when trying to get a corrupt file out of the zip. Other files are working as expected.
The properties for this file are->
(CRC in a working version is: 44D3906C)
Code for processing the doc-template:
/*
* Process the template
*/
function processTemplate(doc64, callback)
{
"use strict";
console.log("PROCESS TEMPLATE");
var XAttribute = Ltxml.XAttribute;
var XCData = Ltxml.XCData;
var XComment = Ltxml.XComment;
var XContainer = Ltxml.XContainer;
var XDeclaration = Ltxml.XDeclaration;
var XDocument = Ltxml.XDocument;
var XElement = Ltxml.XElement;
var XName = Ltxml.XName;
var XNamespace = Ltxml.XNamespace;
var XNode = Ltxml.XNode;
var XObject = Ltxml.XObject;
var XProcessingInstruction = Ltxml.XProcessingInstruction;
var XText = Ltxml.XText;
var XEntity = Ltxml.XEntity;
var cast = Ltxml.cast;
var castInt = Ltxml.castInt;
var W = openXml.W;
var NN = openXml.NoNamespace;
var wNs = openXml.wNs;
var doc = new openXml.OpenXmlPackage(doc64);
// add a paragraph to the beginning of the document.
var body = doc.mainDocumentPart().getXDocument().root.element(W.body);
var tpl_row = ((doc.mainDocumentPart().getXDocument().descendants(W.tbl)).elementAt(1).descendants(W.tr)).elementAt(2);
var newrow = new XElement(tpl_row);
doc.mainDocumentPart().getXDocument().descendants(W.tbl).elementAt(1).add(newrow);
// callback(doc);
var mod_file = null;
var newfile;
var path;
if (doc != null && doc != undefined ) {
mod_file = doc.saveToBlob();
// Start writing document
path = "Templates";
newfile = "Templates/Bau.docx";
console.log("WRITE TEMPLATE DOCUMENT");
fs.root.getFile("Templates/" + "MyGenerated.docx", {create: true, exclusive: false},
function(fileEntry)
{
fileEntry.createWriter(
function(fileWriter)
{
fileWriter.onwriteend = function(e) {
console.log("TEMPLATE DOCUMENT WRITTEN:"+e.target.length);
};
fileWriter.onerror = function(e) {
console.log("ERROR writing DOCUMENT:" + e.code + ";" + e.message);
};
var blobreader = new FileReader();
blobreader.onloadend = function()
{
fileWriter.write(blobreader.result); // reader.result contains the contents of blob as a typed array
};
blobreader.readAsArrayBuffer(mod_file);
},
null);
}, null);
};
Any ideas what I'm doing wrong?
Thanks for posting about the error. There were some issues with jszip.js that I encountered when I was developing the Open XML SDK for JavaScript.
At the following link, there is a sample javascript app that demonstrates generating a document.
Open XML SDK for JavaScript Demo
In that app you can save multiple DOCXs, one after another, and they are not corrupted.
In order to work on this issue, I need to be able to re-produce locally. Maybe you can take that little working web app and replace parts with your parts until it is generating invalid files?
Cheers, Eric
P.S. I am traveling and have intermittent access to internet. If you can continue the thread on OpenXmlDeveloper.org, then it will help me to answer quicker. :-)
What made it work for me, was changing the way of adding images (Parts) to the document. I was using the type "binary" for adding images to document. I changed this to "base64"
So I changed the source from:
mydoc.addPart( "/word/"+reltarget, openXml.contentTypes.png, "binary", fotodata ); // add Image Part to doc
to:
mydoc.addPart( "/word/"+reltarget, openXml.contentTypes.png, "base64", window.btoa(fotodata) ); // add Image Part to doc