How to use JavaScript to implement drag-and-drop adjustment of table column width?

How to use JavaScript to implement drag-and-drop adjustment of table column width?

With the development of Web technology, more and more data are displayed on web pages in the form of tables. However, sometimes the column width of the table cannot meet our needs, and the content may overflow or the width may be insufficient. In order to solve this problem, we can use JavaScript to implement the drag-and-drop adjustment function of the column width of the table, so that users can freely adjust the column width according to their needs.

To implement the drag-and-drop adjustment function of table column width, the following three main steps are required:

1. Mouse event monitoring: It is necessary to add mouse event monitoring to the table in order to capture the user's operation behavior.
2. Dynamic adjustment of column width: Dynamically adjust the width of table columns according to the user's drag operation.
3. Record table status: Record the column width status adjusted by the user so that the adjustment results can be maintained after the page is refreshed or reloaded.

The following will introduce the implementation methods of the above three steps in detail and give corresponding code examples.

1. Mouse event listening

First, add mousedown event listening to the table. When the user clicks on the edge of a table column, they can start dragging to adjust the column width. In the mousedown event handling function, the position of the mouse click needs to be recorded.

function tableMouseDown(event) {
  // 记录鼠标点击的位置
  const startX = event.clientX;
  // ...
}

Next, add the mousemove event listener to the document object. In the mousemove event handler function, you need to calculate the distance moved by the mouse and dynamically change the width of the table column.

function documentMouseMove(event) {
  // 计算鼠标移动的距离
  const distanceX = event.clientX - startX;
  // 动态改变表格列的宽度
  // ...
}

Finally, add a mouseup event listener for the document object. When the user releases the mouse, stop resizing the column width.

function documentMouseUp() {
  // 停止调整列宽
  // ...
}

2. Dynamic adjustment of column width

In the mousemove event handler, dynamically adjust the width of the table column according to the user's drag operation. First, you need to determine which column is currently being dragged, which can be determined through the th element in the header of the table. Then, dynamically change the width of the table column based on the calculated mouse movement distance.

function documentMouseMove(event) {
  // 计算鼠标移动的距离
  const distanceX = event.clientX - startX;
  
  // 动态改变表格列的宽度
  const th = document.elementFromPoint(startX, event.clientY);
  const columnIndex = th.cellIndex;
  const table = th.parentNode.parentNode.parentNode;
  const cells = table.querySelectorAll(`tr th:nth-child(${columnIndex + 1}), tr td:nth-child(${columnIndex + 1})`);

  const newWidth = parseFloat(getComputedStyle(cells[0]).width) + distanceX;
  for (const cell of cells) {
    cell.style.width = `${newWidth}px`;
  }
}

3. Record table status

In order to maintain the column width adjusted by the user after the page is refreshed or reloaded, we need to record the column width status of the table. You can use localStorage or cookie to achieve persistent data storage.

function documentMouseUp() {
  // 停止调整列宽
  // ...

  // 记录表格的列宽状态
  const columnWidths = {};
  const table = document.querySelector('table');
  const columns = table.querySelectorAll('th');
  for (const column of columns) {
    columnWidths[column.cellIndex] = parseFloat(getComputedStyle(column).width);
  }
  
  localStorage.setItem('columnWidths', JSON.stringify(columnWidths));
}

When the page loads, the saved column width state can be read from localStorage and applied to the table.

window.addEventListener('load', function() {
  const columnWidths = JSON.parse(localStorage.getItem('columnWidths'));
  if (columnWidths) {
    const table = document.querySelector('table');
    const columns = table.querySelectorAll('th');
    for (const [index, width] of Object.entries(columnWidths)) {
      columns[index].style.width = `${width}px`;
    }
  }
});

Through the above three steps, we can realize the drag and drop adjustment function of table column width. Users can freely adjust the column width of the table and optimize the display effect of the table according to actual needs. Hope this article is helpful to you!

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