TypeError：无法将属性'innertext'设置为null

Question

我正在开发javascript计算器应用程序。当前，当按下按钮时，出现此错误：

未捕获的TypeError：无法设置innerText的属性'null'

这是我的代码：

class Calculator 
  constructor(previousOperandTextElement, currentOperandTextElement) 
    this.previousOperandTextElement = previousOperandTextElement;
    this.currentOperandTextElement = currentOperandTextElement;
    this.clear();
  
  clear() 
    this.currentOperand = '';
    this.previousOperand = '';
    this.operation = '';
  
  delete() 
  appendNumber(number) 
    this.currentOperand = this.currentOperand.toString() + number.toString();
  
  chooseOperation(operation) 
  computer() 
  updateDisplay() 
    this.currentOperandTextElement.innerText = this.currentOperand;
  

const numberButtons = document.querySelectorAll('[data-number]');
const operationButtons = document.querySelectorAll('[data-operation]');
const equalsButton = document.querySelector(['data-equals']);
const allClearButton = document.querySelector(['data-all-clear']);
const previousOperandTextElement = document.querySelector(['data-previousOperand']);
const currentOperandTextElement = document.querySelector(['data-currentOperand']);
const calculator = new Calculator(previousOperandTextElement, currentOperandTextElement)
numberButtons.forEach(button => 
  button.addEventListener('click', () => 
    calculator.appendNumber(button.innerText)
    calculator.updateDisplay()
  )
)

 <html lang="en">
 <head>
    <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <meta http-equiv="X-UA-Compatible" content="ie=edge">
 <title>Calculator</title>
 <link rel="stylesheet" href="css/style.css">
 </head>
  <body>
     <div class="calculator-grid">
    <div class="output">
        <div data-previousOperand class="previous-operand"></div>
        <div data-currentOperand class="current-operand"></div>
    </div>
    <button data-all-clear class="span-two">AC</button>
    <button data-delete>Del</button>
    <button data-operation>/</button>
    <button data-number>1</button>
    <button data-number>2</button>
    <button data-number>3</button>
    <button data-operation>*</button>
    <button data-number>4</button>
    <button data-number>5</button>
    <button data-number>6</button>
    <button data-operation>+</button>
    <button data-number>7</button>
    <button data-number>8</button>
    <button data-number>9</button>
    <button data-operation>-</button>
    <button data-number>.</button>
    <button data-number>0</button>
    <button data-equals class="span-two">=</button>
    </div>
    <script src="js/index.js"></script>
    </body>
    </html>