I am getting the error TypeError: Cannot set properties of undefined and am unsure why.

let studentName = "";
var ID;
let studentClass;
let faculty="";
IDarray = [[studentName , ID , studentClass , faculty]]; // <--defined here

Then at this point below, the array is in a for-loop and the variables 'e.g. studentName' have values.

for(let i = 0; i < 2; i++){

*...variables with their values...*

IDarray[i][0] = [studentName , ID , studentClass , faculty]; //<--throwing error?!?

}