用JavaScript写一个计算器

好的，我可以回答这个问题。以下是一个简单的JavaScript计算器代码：

HTML代码：

<div>
  <input type="text" id="result" readonly>
</div>
<div>
  <button onclick="clearResult()">C</button>
  <button onclick="deleteLast()">←</button>
  <button onclick="calculate('/')">÷</button>
  <button onclick="calculate('*')">x</button>
</div>
<div>
  <button onclick="addNumber(7)">7</button>
  <button onclick="addNumber(8)">8</button>
  <button onclick="addNumber(9)">9</button>
  <button onclick="calculate('-')">-</button>
</div>
<div>
  <button onclick="addNumber(4)">4</button>
  <button onclick="addNumber(5)">5</button>
  <button onclick="addNumber(6)">6</button>
  <button onclick="calculate('+')">+</button>
</div>
<div>
  <button onclick="addNumber(1)">1</button>
  <button onclick="addNumber(2)">2</button>
  <button onclick="addNumber(3)">3</button>
  <button onclick="calculate('=')">=</button>
</div>
<div>
  <button onclick="addNumber()"></button>
  <button onclick="addNumber('.')">.</button>
</div>

JavaScript代码：

let num1 = '';
let num2 = '';
let operator = '';
let result = document.getElementById('result');

function addNumber(num) {
  if (operator === '') {
    num1 += num;
    result.value = num1;
  } else {
    num2 += num;
    result.value = num2;
  }
}

function calculate(op) {
  if (num1 === '' || num2 === '') {
    return;
  }
  let res;
  switch (operator) {
    case '+':
      res = parseFloat(num1) + parseFloat(num2);
      break;
    case '-':
      res = parseFloat(num1) - parseFloat(num2);
      break;
    case '*':
      res = parseFloat(num1) * parseFloat(num2);
      break;
    case '/':
      res = parseFloat(num1) / parseFloat(num2);
      break;
  }
  num1 = res.toString();
  num2 = '';
  operator = op;
  result.value = num1;
}

function clearResult() {
  num1 = '';
  num2 = '';
  operator = '';
  result.value = '';
}

function deleteLast() {
  if (operator === '') {
    num1 = num1.slice(, -1);
    result.value = num1;
  } else {
    num2 = num2.slice(, -1);
    result.value = num2;
  }
}

这个计算器可以进行加、减、乘、除四则运算，也支持小数点和清空操作。