将下面这个list渲染成表格，在下面显示总价， 总价可以使用reduce计算

 <script>
    var list = [
      {
        "title": "笔",
        "price": 2,
        "num": 2
      },
      {
        "title": "本",
        "price": 1,
        "num": 3
      },
      {
        "title": "尺子",
        "price": 3,
        "num": 1
      }
    ]
    var str = '<table><tr><th>编号</th><th>物品</th><th>价格</th><th>数量</th></tr>'

    list.forEach(function (item, index) {
      str += '<tr>'
      str += '<td>' + (index + 1) + '</td>'
      for (var key in item) {
        str += '<td>' + item[key] + '</td>'
      }
      str += '</tr>'
    })
    str += '</table>'

    document.write(str)

    var sum = list.reduce(function (res, curr) {
      // console.log(res, curr.price, curr.num)
      return res += curr.price * curr.num
    }, 0)
    // console.log(sum)
    document.write('总价：' + sum)

  </script>