I'm using an object oriented chart and setting data according to the scroll position. I'm using d3.csv() to load data with then(), like this:

const chart = new Chart(instatiatechartfunctions);

let dataObj1 = d3.csv('datapath', dataparsefunction);
let dataObj2 = d3.csv('datapath2', dataparsefunction);

let dataArr = [dataObj1,dataObj2];

function init(data){
     chart.setData(data);
    }

let g3 = scrollerfunction().settings()
                           .on('active', function(i){
                                dataArr[i].then(init); //error here
                                });

It's quite complicated for me to include the scroller library along with all the code for the chart, so I hope the above is clear enough. My main issue is that calling init in then() with no () shows the graph but returns the error in the title. when I use the parentheses (then(init())) I get the following error:

Uncaught TypeError: Cannot read properties of undefined (reading '0')

I am using d3.v6 Can anyone help?