Create and Save a File With JavaScript

Javascript: a SIMPLE way to save a text file?

You can do it this way:

<a href="#" id="download">Download</a>

<script>
var fileName = "myfile.txt";
var fileContent = "Page content...";
var myFile = new Blob([fileContent], {type: 'text/plain'});

window.URL = window.URL || window.webkitURL;
var dlBtn = document.getElementById("download");

dlBtn.setAttribute("href", window.URL.createObjectURL(myFile));
dlBtn.setAttribute("download", fileName);
</script>

This will ask the user to save a file called "myfile.txt" where they'd like to. The contents of the file is up to you.

Using HTML5/JavaScript to generate and save a file

OK, creating a data:URI definitely does the trick for me, thanks to Matthew and Dennkster pointing that option out! Here is basically how I do it:

1) get all the content into a string called "content" (e.g. by creating it there initially or by reading innerHTML of the tag of an already built page).

2) Build the data URI:

uriContent = "data:application/octet-stream," + encodeURIComponent(content);

There will be length limitations depending on browser type etc., but e.g. Firefox 3.6.12 works until at least 256k. Encoding in Base64 instead using encodeURIComponent might make things more efficient, but for me that was ok.

3) open a new window and "redirect" it to this URI prompts for a download location of my JavaScript generated page:

newWindow = window.open(uriContent, 'neuesDokument');

That's it.

Is it possible to write data to file using only JavaScript?

Some suggestions for this -

1. If you are trying to write a file on client machine, You can't do this in any cross-browser way. IE does have methods to enable "trusted" applications to use ActiveX objects to read/write file.
2. If you are trying to save it on your server then simply pass on the text data to your server and execute the file writing code using some server side language.
3. To store some information on the client side that is considerably small, you can go for cookies.
4. Using the HTML5 API for Local Storage.

How to create a file in memory for user to download, but not through server?

You can use data URIs. Browser support varies; see Wikipedia. Example:

<a href="data:application/octet-stream;charset=utf-16le;base64,//5mAG8AbwAgAGIAYQByAAoA">text file</a>

The octet-stream is to force a download prompt. Otherwise, it will probably open in the browser.

For CSV, you can use:

<a href="data:application/octet-stream,field1%2Cfield2%0Afoo%2Cbar%0Agoo%2Cgai%0A">CSV Octet</a>

Try the jsFiddle demo.

how to save and read file from %temp% using node js?

os.tmpdir() returns the operating system's default directory for temporary files as a string

const os = require('os');

os.tmpdir();

How do I let user save a file and keep editing that file in browser Javascript only?

You can use localStorage to achieve this without needing any other permission from the user.

localStorage.setItem("data", JSON.stringify(data));

If your data is just JSON then this would work, however if you have custom data types, you can take a look here.

Edit:

Since you wanted to save the file directly to the device and edit it, you can take a look at File System Access API. This article here explains it.

You can load the file first by using,

let fileHandle;
butOpenFile.addEventListener('click', async () => {
  [fileHandle] = await window.showOpenFilePicker();
  const file = await fileHandle.getFile();
  const contents = await file.text();
  textArea.value = contents;
});

Once you have the file handle you should be able to write to the file without requesting to download a new file everytime there is a change.

async function writeFile(fileHandle, contents) {
  // Create a FileSystemWritableFileStream to write to.
  const writable = await fileHandle.createWritable();
  // Write the contents of the file to the stream.
  await writable.write(contents);
  // Close the file and write the contents to disk.
  await writable.close();
}

The codes are from the article I have linked above and the article explains everything much clearly. It's worth reading.

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