I am using the following code to try and create a file in the user's temp folder, but it will not.

    var fs = require('fs');
    var os = require('os');
    var ostemp = os.tmpdir();
    var exec = require('child_process').exec;
    var file = fs.createWriteStream(ostemp + '\setup.exe');

ostemp will return a path similar to 'c:\users\user\appdata\local\temp'

But the code above will save the file to local, and the filename will be tempsetup.exe

Why is that?