So I have Odoo module where I want to retrieve a PDF report. I already figured out how to download the report the easy way with the following. Mind you I'm already using that for something is a POS module.

var link = document.createElement('a');
link.href = "http://" + window.location.host + "/report/pdf/account.report_invoice/" + res;
link.download = 'file.pdf';
link.dispatchEvent(new MouseEvent('click'));

But what I need it to get the PDF data, in base64 would be fine too. I tried a fetch request to the report url like the following:
fetch('http://10.5.1.49:8070/report/pdf/nrg_labels.report_reorder/1', {
   mode: "no-cors",
   redirect: "follow",
   method: 'GET',
   headers: {
      "Content-Type": "application/pdf",
   },
}).then(function(response){
   console.log("Response from fetch: ", response);
   return response.blob();          
}).then(function(blob){
   getBase64(blob).then(function(base64){
      console.log("getBase64 Response: ", base64);
      startConnection({ retries: 5, delay: 1 }, base64);    
   });
});
The above doesn't properly return the PDF data. The response comes back with a status of zero.
I've looked around in the source code to see how they do it. 

function getReport(){
    rpc.query({
        model: 'nrg_labels.nrg_labels',
        method: 'get_report',
        args: [1]
    }).then(function(data){
        console.log('NRG Labels PDF: ', data);
        startConnection({ retries: 5, delay: 1 }, data);
    });
}


I tried the above based on something I saw in the source code. I can't get it to work. 

So the questions is, how can I retrieve the report PDF data, preferably in a way I can get any report?
Any help is appreciated. Thanks