HTML

<table>
    <tr>
      <th class="allCheck">
        <input type="checkbox" name="" id="checkAll"> <span class="all">全选</span>
      </th>
      <th>商品</th>
      <th>商家</th>
      <th>价格</th>
    </tr>
    <tr>
      <td>
        <input type="checkbox" name="check" class="ck">
      </td>
      <td>小米手机</td>
      <td>小米</td>
      <td>￥1999</td>
    </tr>
    <tr>
      <td>
        <input type="checkbox" name="check" class="ck">
      </td>
      <td>小米净水器</td>
      <td>小米</td>
      <td>￥4999</td>
    </tr>
    <tr>
      <td>
        <input type="checkbox" name="check" class="ck">
      </td>
      <td>小米电视</td>
      <td>小米</td>
      <td>￥5999</td>
    </tr>
  </table>

CSS

 * {
      margin: 0;
      padding: 0;
    }

    table {
      border-collapse: collapse;
      border-spacing: 0;
      border: 1px solid #c0c0c0;
      width: 500px;
      margin: 100px auto;
      text-align: center;
    }

    th {
      background-color: #09c;
      font: bold 16px "微软雅黑";
      color: #fff;
      height: 24px;
    }

    td {
      border: 1px solid #d0d0d0;
      color: #404060;
      padding: 10px;
    }

    .allCheck {
      width: 80px;
    }

JS

//获取全选多选框
    const ck = document.querySelector('#checkAll')
    //获取每行的多选框
    const cks = document.querySelectorAll('.ck')

    //全选添加事件
    ck.addEventListener('click',function(){
      for(let i = 0;i<cks.length;i++){
        cks[i].checked = ck.checked;
      }
    })
    //给每行的多选框做个判断
    //利用属性选择器获取所有已选的多选框是否等于所有多选框的个数
    //如果相同就判定为全选
    for(let i = 0;i<cks.length;i++){
        cks[i].addEventListener('click',function(){
         ck.checked = document.querySelectorAll('.ck:checked').length === cks.length
        })
      }

效果