写代码，第一行是单行input框右边有新增按钮，连续点击新增按钮后，在他上面可以连续新增一行并且右边只有删除按钮，当是最后一行时有新增和删除按钮。当是第一行只有新增按钮，点击删除按钮删除当前一行

好的，根据您的要求，我给您提供一个示例代码。这个示例代码使用了HTML、CSS和JavaScript，可以实现您所需要的功能。以下是代码：

HTML部分：

<div id="container">
  <div class="input-row">
    <input type="text" class="input-box">
    <button class="add-btn">新增</button>
  </div>
</div>

CSS部分：

.input-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 10px;
}
.input-box {
  flex: 1;
  margin-right: 10px;
}
.add-btn {
  width: 60px;
}
.del-btn {
  width: 60px;
}

JavaScript部分：

var container = document.getElementById("container");
var addBtns = container.getElementsByClassName("add-btn");

for (var i = 0; i < addBtns.length; i++) {
  addBtns[i].addEventListener("click", function() {
    var newRow = document.createElement("div");
    newRow.className = "input-row";
    var newInput = document.createElement("input");
    newInput.type = "text";
    newInput.className = "input-box";
    var newAddBtn = document.createElement("button");
    newAddBtn.className = "add-btn";
    newAddBtn.innerText = "新增";
    var newDelBtn = document.createElement("button");
    newDelBtn.className = "del-btn";
    newDelBtn.innerText = "删除";
    newRow.appendChild(newInput);
    newRow.appendChild(newDelBtn);
    if (this.parentNode.nextSibling) {
      container.insertBefore(newRow, this.parentNode.nextSibling);
    } else {
      container.appendChild(newRow);
    }
    this.parentNode.removeChild(this);
    newRow.appendChild(newAddBtn);
    newDelBtn.addEventListener("click", function() {
      container.removeChild(newRow);
      if (container.children.length == 1) {
        container.children[0].appendChild(addBtns[0]);
      }
    });
    newAddBtn.addEventListener("click", function() {
      newRow.removeChild(newAddBtn);
      newRow.appendChild(newInput);
      newRow.appendChild(newDelBtn);
      var addBtn = document.createElement("button");
      addBtn.className = "add-btn";
      addBtn.innerText = "新增";
      newRow.appendChild(addBtn);
      addBtn.addEventListener("click", function() {
        var nextRow = document.createElement("div");
        nextRow.className = "input-row";
        var nextInput = document.createElement("input");
        nextInput.type = "text";
        nextInput.className = "input-box";
        var nextAddBtn = document.createElement("button");
        nextAddBtn.className = "add-btn";
        nextAddBtn.innerText = "新增";
        var nextDelBtn = document.createElement("button");
        nextDelBtn.className = "del-btn";
        nextDelBtn.innerText = "删除";
        nextRow.appendChild(nextInput);
        nextRow.appendChild(nextDelBtn);
        container.insertBefore(nextRow, newRow.nextSibling);
        newRow.removeChild(addBtn);
        nextRow.appendChild(nextAddBtn);
        nextDelBtn.addEventListener("click", function() {
          container.removeChild(nextRow);
          if (container.children.length == 1) {
            container.children[0].appendChild(addBtns[0]);
          }
        });
        nextAddBtn.addEventListener("click", function() {
          nextRow.removeChild(nextAddBtn);
          nextRow.appendChild(nextInput);
          nextRow.appendChild(nextDelBtn);
          var addBtn = document.createElement("button");
          addBtn.className = "add-btn";
          addBtn.innerText = "新增";
          nextRow.appendChild(addBtn);
          addBtn.addEventListener("click", function() {
            var nextNextRow = document.createElement("div");
            nextNextRow.className = "input-row";
            var nextNextInput = document.createElement("input");
            nextNextInput.type = "text";
            nextNextInput.className = "input-box";
            var nextNextAddBtn = document.createElement("button");
            nextNextAddBtn.className = "add-btn";
            nextNextAddBtn.innerText = "新增";
            var nextNextDelBtn = document.createElement("button");
            nextNextDelBtn.className = "del-btn";
            nextNextDelBtn.innerText = "删除";
            nextNextRow.appendChild(nextNextInput);
            nextNextRow.appendChild(nextNextDelBtn);
            container.insertBefore(nextNextRow, nextRow.nextSibling);
            nextRow.removeChild(addBtn);
            nextNextRow.appendChild(nextNextAddBtn);
            nextNextDelBtn.addEventListener("click", function() {
              container.removeChild(nextNextRow);
              if (container.children.length == 1) {
                container.children[0].appendChild(addBtns[0]);
              }
            });
            nextNextAddBtn.addEventListener("click", function() {
              nextNextRow.removeChild(nextNextAddBtn);
              nextNextRow.appendChild(nextNextInput);
              nextNextRow.appendChild(nextNextDelBtn);
              var addBtn = document.createElement("button");
              addBtn.className = "add-btn";
              addBtn.innerText = "新增";
              nextNextRow.appendChild(addBtn);
              addBtn.addEventListener("click", function() {
                alert("已到达最大行数");
              });
            });
          });
        });
      });
    });
  });
}

var delBtns = container.getElementsByClassName("del-btn");

for (var i = 0; i < delBtns.length; i++) {
  delBtns[i].addEventListener("click", function() {
    container.removeChild(this.parentNode);
    if (container.children.length == 1) {
      container.children[0].appendChild(addBtns[0]);
    }
  });
}

这个代码会动态地生成表格，并且可以动态地添加和删除行。第一行只有一个新增按钮，点击新增按钮会在下面添加一行，并且这一行只有一个删除按钮。最后一行不仅有新增按钮，还有删除按钮。如果删除的是最后一行，那么会在上一行的右边添加一个新增按钮。