function calculate() let result = eval(prev + lastOp + current); // simplistic display = result; waitingForOperand = true;
let display = "0"; let memory = 0; let lastOp = null; let waitingForOperand = false; function inputDigit(d) /* handle overflow, leading zero */ function inputOperation(op) if (!waitingForOperand) calculate(); lastOp = op; waitingForOperand = true;
End of guide. Now go calculate something simple.