How to use CSS to control the visibility of web page elements

In web design, CSS is an integral part of controlling page style. In addition to setting the appearance of a web page, CSS can also set the visibility of elements. This article will introduce you to how to use CSS to control the visibility of web page elements, and how to apply it in actual projects.

1. CSS sets the visibility of elements

CSS provides two properties to control the visibility of elements: visibility and display. Their uses and effects are different, and we will introduce them separately below.

1. visibility attribute

The visibility attribute is used to set the visibility of the element. It has the following attribute values:

visible (default value): element Visible;

hidden: The element is invisible, but still retains the space it occupies;

collapse: only used for table elements, folding the rows or columns of the table, and normal content will not be displayed .

For example, we can set visibility:hidden for a div to make it invisible:

div {
  visibility: hidden;
}

2. display attribute

The display attribute is used to set the element The display mode has the following attribute values:

block: The element is displayed at the block level and occupies one or more lines;

inline: The element is displayed inline and displayed side by side with other inline elements. ;

inline-block: The element is displayed at the inline block level, displayed side by side with other inline elements, but attributes such as width and height can be set;

none: The element is not visible and will not Retain the space it occupies.

For example, we can set display:none for a span to make it invisible:

span {
  display: none;
}

2. CSS application example

1. "Back to top" button

We can often see the existence of the "Back to Top" button on some websites. At this time, we can use visibility control to only display the button when the page scroll bar has scrolled to a certain position.

HTML part:

<a href="#" id="back-to-top">返回顶部</a>

CSS part:

#back-to-top {
  position: fixed;
  bottom: 50px;
  right: 50px;
  display: none;
}

#back-to-top.show {
  display: block;
}

JavaScript (jQuery) part:

$(window).scroll(function() {
  if ($(this).scrollTop() > 500) {
    $('#back-to-top').addClass('show');
  } else {
    $('#back-to-top').removeClass('show');
  }
});

The above code listens to the position of the page scroll bar, Show the "Back to top" button when it exceeds 500 pixels, otherwise hide the button.

2. The "show/hide" function of the table

In some cases where the amount of data in the table is large, we can use visibility control to realize the "show/hide" function of the table. Hide" function to improve user experience.

HTML part:

<button id="toggle-table">显示/隐藏表格</button>

<table id="data">
  <thead>
    <tr>
      <th>姓名</th>
      <th>年龄</th>
      <th>性别</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>小红</td>
      <td>20</td>
      <td>女</td>
    </tr>
    <tr>
      <td>小明</td>
      <td>22</td>
      <td>男</td>
    </tr>
  </tbody>
</table>

CSS part:

#data {
  display: none;
}

JavaScript (jQuery) part:

$('#toggle-table').click(function() {
  $('#data').toggle();
});

In the above code, we set the display:none to make it initially invisible. Then, in JavaScript, we use the toggle() method to toggle the visibility of the table when the user clicks the "Show/Hide Table" button.

3. Notes

1. After setting display:none, the element will not retain the space it occupies. Therefore, when you need to use this element, dynamically change it to display:block or other value in JavaScript.
2. The visibility of an element may be affected by settings on parent or ancestor elements. For example, when the parent element is set to visibility:hidden, the child elements will also be invisible.
3. Don't abuse the visibility control of elements, it should be set according to actual needs. Excessive use of visibility controls can lead to code clutter and poor performance.

Summary

In this article, we learned how to use CSS to control the visibility of web page elements. In addition to improving the interactivity and user experience of the page, controlling the visibility of elements can also effectively save the resource overhead of the page. Therefore, in actual projects, we should flexibly apply CSS to set the visibility of elements.

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