Load array declaration from a text file in JavaScript

Before posting, I've read through suggested similar questions, but couldn't find an answer.

I have an array declaration stored in a text.txt file. Let's say the array declaration looks something like this:

["content1-1", ["content2-1", "content2-1"]]

I want to load this as an array into a variable in JavaScript.

This is what I tried:

var data = []

	function loadSOAFile(chineseCharacter) {
		var textfileFileName = "text.txt"
		var rawSOAFile=new XMLHttpRequest();
		rawSOAFile.open("GET",textfileFileName);
		rawSOAFile.onload=function(){
    			console.log(rawSOAFile.responseText);
			data = rawSOAFile.responseText
		}
		rawSOAFile.send();
		
		setTimeout(function() {
                     document.getElementById("debuggingconsole").innerHTML = data[0]
    }, 200);
}

However, when I call the function, instead of writing "content1-1" it writes "[", so clearly it loads the variable as a string rather than an array.

Is there a cleaver way to load it as an array declaration? I don't deal with JS all that often, so answers providing a little bit more context would be most appreciated.