How to call a column in JS DDX bricks

Hi,

I wrote this script to switch the sentence on a landing page to switch every 5 seconds. It currently does that. However, as soon as I insert the column data it no longer reads the first sentence and doesn't switch sentences. What might I be doing wrong? Still learning JS so I appreciate the help. The script works but as soon as I try to input the display name it breaks.

var columnData = input['Display Name'];
var header = document.getElementById('header');
var sentences = [
'Hello ' + columnData[0], //This is no longer displayed (if i remove columndata[0] it works.
'What KPI group would you like to view?'
];
var sentenceIndex = 0;

function changeHeader() {
header.innerHTML = sentences[sentenceIndex];
sentenceIndex = (sentenceIndex + 1) % sentences.length;
}

// Initial call to display the first sentence
changeHeader();

// Set interval to change header text every 5 seconds
setInterval(changeHeader, 5000);