javascript select all cancel

JavaScript is a widely used scripting language that is often used for front-end web development. In web development, it often involves the implementation of the select all and deselect all functions. At this time, we usually need to use JavaScript. This article will introduce how to use JavaScript to implement the select all and deselect all functions.

1. HTML code

Before implementing the select all and deselect all functions, we need to write the HTML code first. The following is a sample HTML code, including the table header and content:

<div class="tableContainer">
  <table>
    <thead>
      <tr>
        <th><input type="checkbox" id="selectAll"/>javascript select all cancel</th>
        <th>姓名</th>
        <th>年龄</th>
        <th>性别</th>
      </tr>
    </thead>
    <tbody>
      <tr>
        <td><input type="checkbox" class="checkbox"/></td>
        <td>张三</td>
        <td>20</td>
        <td>男</td>
      </tr>
      <tr>
        <td><input type="checkbox" class="checkbox"/></td>
        <td>李四</td>
        <td>25</td>
        <td>男</td>
      </tr>
      <tr>
        <td><input type="checkbox" class="checkbox"/></td>
        <td>王五</td>
        <td>30</td>
        <td>女</td>
      </tr>
    </tbody>
  </table>
</div>

In the table header, we added a select-all checkbox, set its id to "selectAll", and set the id of each row in the other rows. A checkbox is also added to the first cell and its class is set to "checkbox".

2. JavaScript code

Next, we need to write JavaScript code to implement our functions. We need to add events to the select all checkbox at the head of the table and the checkbox of each row to implement the functions of selecting all and deselecting all. The following is the JavaScript code:

<script>
  // 获取表格头部的javascript select all cancelcheckbox
  var selectAll = document.getElementById("selectAll");
  // 获取每一行中的checkbox
  var checkboxes = document.getElementsByClassName("checkbox");
 
  // 给表格头部的javascript select all cancelcheckbox绑定点击事件
  selectAll.onclick = function() {
    // 循环遍历每一行的checkbox
    for(var i=0; i < checkboxes.length; i++) {
      // 将每一行的checkbox的选中状态设置为表格头部的javascript select all cancelcheckbox的选中状态
      checkboxes[i].checked = selectAll.checked;
    }
  }
 
  // 循环遍历每一行的checkbox
  for(var i=0; i < checkboxes.length; i++) {
    // 给每一个checkbox绑定点击事件
    checkboxes[i].onclick = function() {
      // 定义一个变量，表示是否所有行中的checkbox都被选中
      var isCheckedAll = true;
      // 循环遍历每一行的checkbox
      for(var j=0; j < checkboxes.length; j++) {
        // 如果有一个checkbox没有被选中，将isCheckedAll设置为false
        if(!checkboxes[j].checked) {
          isCheckedAll = false;
          break;
        }
      }
      // 将表格头部的javascript select all cancelcheckbox的选中状态设置为isCheckedAll
      selectAll.checked = isCheckedAll;
    }
  }
</script>

3. Implement the effect

After the HTML and JavaScript codes are completed, we can implement the functions of selecting all and deselecting all.

When the user checks the Select All checkbox at the header of the table, the checkboxes in all rows will be automatically checked:

When the user unchecks the checkbox When selecting the Select All checkbox at the header of the table, the checkboxes in all rows will be automatically unchecked:

And when the user checks or unchecks the checkbox of a certain row When and how to cancel the select all function. By writing HTML and JavaScript code, we can easily implement the functions of selecting all and deselecting all, thereby improving the user experience of the web page.

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