Save Data directly to the local file system [Archive]

KevinJohnson

05-18-2009, 01:09 PM

This is a piece of code that is an essential for creating SPAs (Single Page Applications - e.g. Tiddlywiki) or DHTML Applications. What it does is allow you to save data directly to the local filesystem.

Notes:
1. This only works under Geko (Firefox, and Mozilla)
2. The webpage that uses this must be run from the local file system, otherwise an error will be thrown.
3. Even though there is a textbox for changing the file name and path to save to, i didn't write the code that will change it. I hard-coded the file name into the JavaScript code. I'm sure you can figure out how to change it.

<html>
<head>
<script language="javascript">
var savefile = "c:\mozdata.txt";

function save() {
try {
netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
} catch (e) {
alert("Permission to save file was denied.");
}
var file = Components.classes["@mozilla.org/file/local;1"]
.createInstance(Components.interfaces.nsILocalFile);
file.initWithPath( savefile );
if ( file.exists() == false ) {
alert( "Creating file... " );
file.create( Components.interfaces.nsIFile.NORMAL_FILE_TYPE, 420 );
}
var outputStream = Components.classes["@mozilla.org/network/file-output-stream;1"]
.createInstance( Components.interfaces.nsIFileOutputStream );

outputStream.init( file, 0x04 | 0x08 | 0x20, 420, 0 );
var output = document.getElementById('FileData').value;
var result = outputStream.write( output, output.length );
outputStream.close();

}
function read() {
try {
netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
} catch (e) {
alert("Permission to read file was denied.");
}
var file = Components.classes["@mozilla.org/file/local;1"]
.createInstance(Components.interfaces.nsILocalFile);
file.initWithPath( savefile );
if ( file.exists() == false ) {
alert("File does not exist");
}
var is = Components.classes["@mozilla.org/network/file-input-stream;1"]
.createInstance( Components.interfaces.nsIFileInputStream );
is.init( file,0x01, 00004, null);
var sis = Components.classes["@mozilla.org/scriptableinputstream;1"]
.createInstance( Components.interfaces.nsIScriptableInputStream );
sis.init( is );
var output = sis.read( sis.available() );
document.getElementById('FileData').value = output;
}
</script>
</head>

<body>
<b>File Name:</b>
<br>
<input id="filename" type="text">
<br>
<br>
<b>Data:</b><br>
<textarea id="FileData" height="50" width="50"></textarea>
<br>
<br>
<input type="button" value="Save" OnClick="save()">
<input type="button" value="Load" OnClick="read()">
<br>
<br>
<input type="reset" value="Reset">

</body>
</html>