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CSS

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:Checked

The :checked pseudo-class in CSS is used to select and style form elements like radio buttons, checkboxes, and options in a select element that are in a selected or "checked" state. This allows you to provide visual feedback to users when they interact with these input types.

Example 1: Styling a Checked Checkbox

/* This CSS rule targets a checkbox input when it is checked. */
input[type="checkbox"]:checked {
  /* The box-shadow property adds a blue glow around the checkbox. */
  box-shadow: 0 0 5px 2px dodgerblue;
}

Explanation

This code applies a blue shadow around a checkbox when the user clicks on it. The input[type="checkbox"] part selects all checkboxes, and the :checked pseudo-class narrows that down to only the one that is currently checked.

Example 2: Revealing Content When a Radio Button is Checked

/* This CSS hides a div by default. */
.hidden-content {
  display: none;
}

/* When the radio button with the id 'show' is checked, the adjacent .hidden-content div is displayed. */
#show:checked ~ .hidden-content {
  display: block;
}

Explanation

This example demonstrates how to show a hidden element when a specific radio button is selected. The ~ is the general sibling combinator, which selects the .hidden-content div that follows the checked radio button.

Example 3: Changing the Label Style of a Checked Option

/* This CSS rule targets the label of a checked radio button. */
input[type="radio"]:checked + label {
  /* The color property changes the text color to green. */
  color: green;
  /* The font-weight property makes the text bold. */
  font-weight: bold;
}

Explanation

This code changes the text color and weight of a label associated with a radio button when that button is selected. The + is the adjacent sibling combinator, selecting the label that immediately follows the checked radio button.

Example 4: Custom Styled Checkbox

/* This CSS creates a custom styled checkbox. */
.custom-checkbox:checked {
  background-color: #2196F3; /* Blue background when checked */
  border-color: #2196F3;
}

.custom-checkbox:checked::before {
  content: '\2713'; /* Adds a checkmark character */
  display: block;
  color: white;
  text-align: center;
}

Explanation

This CSS provides a more customized look for a checkbox. When the checkbox is checked, its background color changes, and a checkmark character is inserted using the ::before pseudo-element.

Example 5: Highlighting a selected option in a dropdown

/* This rule styles the selected option within a select element. */
option:checked {
    background: linear-gradient(to right, #66bb6a, #43a047); /* Green gradient background */
    color: white; /* White text color */
}

Explanation

This code enhances the user experience of a dropdown menu by styling the currently selected <option>. It applies a green gradient background and white text to the option that has been :checked.