Here's the code:

function populateTotal() {
  // reduce transaction amounts to a single total value
  let total = transactions.reduce((total, t) => {
    return total + parseInt(t.value);
  }, 0);

  let totalEl = document.querySelector("#total");
  totalEl.textContent = total;
}

Getting this error on the deployed app:

Uncaught (in promise) TypeError: transactions.reduce is not a function;