根据PapaParser Docs，你需要传入一个js文件对象或CSV字符串。

// file is a File object obtained from the DOM.
// config is a config object which contains a callback.
// Doesn't return anything. Results are provided asynchronously to a callback function.

Papa.parse(file, config)

JS：使用Async/Await

const csv = await fetch('/headlines.csv').then( res => res.text() );

Papa.parse( csv, {
    download: true,
    complete: function(results, file) {
        console.log("Parsing complete:", results, file);
    }
});

JS：使用Promises

fetch('/headlines.csv')
    .then( res => res.text() )
    .then( csv => {
        Papa.parse( csv, {
            download: true,
            complete: function(results, file) {
                console.log("Parsing complete:", results, file);
            }
        });
    });