How to decode a base64 string properly in javascript

I tried to convert a base64 string generated from pdf file using FileReader.readAsDataURL() to its original format.
In NodeJS I did it like this and it was able generated the pdf to its initial state.

filebuffer = "data:application/pdf;base64,JVBERi0xLjQKJSDi48/..........."
let base64file = fileBuffer.split(';base64,').pop();
fs.writeFileSync('download.pdf',base64file,{encoding:'base64'},function(err){
    if(err === null){
        console.log("file created");
        return;
    }
    else{
        console.log(err);
        return;
    }
})

But i tried to do it in HTML + Javascript in this way.But in this way , pdf was empty/no letter wasn't in it

let stringval = "data:application/pdf;base64,JVBERi0xLjQKJSDi48/..........."
let encodedString = stringval.split(';base64,').pop();

let data = atob(encodedString);
let blob = new Blob([data]);

// //if you need a literal File object
let file = new File([blob], "filename");

link.href = URL.createObjectURL(file);
link.download = 'filename';

what i am doing wrong .. and how to solve it?