If you are using HTML and CSS, the following should do the trick:

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ul {
    text-align: center;
} 
li {
    display: inline-block; 
}

This will align all list elements in the center of the page.

For more information, please see this tutorial.

To embed a video into an HTML page, you can use the <video> element. The src attribute is used to provide the location of the video, which must have one of the following formats: .mp4, .ogg, .webm. You can also use the <source> element as a child of the <video> element to specify one or more sources for the video. For example:

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<video width="320" height="240" controls>
  <source src="/assets/video.mp4" type="video/mp4">
  <source src="/assets/video.ogg" type="video/ogg">
  <source src="/assets/video.webm" type="video/webm">
  Your browser does not support the video tag.
</video>

For more information, please refer to the W3C HTML documentations.

You can change the class of an HTML element using JavaScript Selectors. To change an element's class, use the classList method. The .toggle() method can be used to add or remove a class from an element:

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document.querySelector("#element").classList.toggle("classname");

This statement will add the specified class to the element if it does not already have the class, or remove it if the element already had the class.

You can also use the .add() and .remove() methods to add or remove a single class from an element, respectively:

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document.querySelector("#element").classList.add("classname");
document.querySelector("#element").classList.remove("classname");

For more information, see MDN's documentation on classList.

You can change an HTML element text inside React using setState(). This can be done by calling the function and then setting the new value for HTML elements like h2 as shown in the example below.

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class App extends React.Component {
  constructor(props) {
    super(props);
    this.state = { 
        text: 'Hello world!'
    }
  }

  handleTextChange = () => {
      this.setState({text: 'This is my new text!'});
  }

  render() {
    return (
      <div>
        <h2>{this.state.text}</h2>
        <button onClick={this.handleTextChange}>Change text</button>
      </div>
    )
  }
}

You can read more about this use case in this article.

You can use the box-shadow CSS property to add a shadow to an HTML element, like a div. Here is an example:

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div {
  box-shadow: 10px 5px 3px 0px rgba(0,0,0,0.3);
}

This will give the div a shadow that is 10px in the x-direction, 5px in the y-direction, has a blur radius of 3px, and has an opacity of 0.3.

More information about the box-shadow property can be found at MDN's web docs.

Yes, you can add an href attribute to an element within an if statement in JavaScript. Here's an example:

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let someCondition = true;

if (someCondition) {
  let element = document.createElement('a');

  element.innerText = 'Click me';
  element.href = 'https://example.com/';

  document.querySelector('body').appendChild(element);
}

The :last-child selector in CSS filters elements that are the last child of their parent. This can be very useful when working with block elements.

For example:

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div:last-child {
    font-weight:bold;
}

In this CSS, all divs that are the :last-child of their parent would have a font weight of bold.

More information can be found here.

To remove an array in most programming languages, you can use the pop() or shift() command depending on whether you want to remove the first or last element in the array. For instance, in JavaScript, you can use the following command to remove the last element of the myArray array:

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myArray.pop()

For more information on these commands, please refer to the Mozilla Developer Network documentation.

You can use an array to set the innerHTML of an element to the correct day of the week by first declaring and initializing an array containing the days of the week. For example:

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let days = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"];

Then you can use the getDay() method to get the index of the day in the array, like so:

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let index = new Date().getDay();

Finally, you can use the calculated index value to access the appropriate day of the week string from the array, and set it as the value of the element's innerHTML:

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document.getElementById("elementId").innerHTML = days[index];

You can find more information on the getDay() here.

You can use the CSS opacity property to create a transparent element. opacity is a value between 0 (fully transparent) and 1 (fully opaque). For example:

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element {
    opacity: 0.5;
}

More information can be found here.

To make an element with opacity 50% but have the text inside be full opacity you can use the CSS opacity and rgba property, such as:

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.element {
  opacity: 0.5;
  color: rgba(0, 0, 0, 1);
}

This creates an element with 50% opacity while the text inside the element will be fully opaque. More information on rgba and opacity can be found on the MDN Web Docs.

In CSS, padding is the space between an element's border and its content. By specifying a padding value, we can control how much space is added around an element's content. The syntax for padding is padding: top right bottom left;, or a single value to apply the same padding on all four sides of an element. In the following example, padding of 10px has been applied to an element:

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.element {
    padding: 10px;
}

If only two values are specified, the first value applies to the top and bottom, and the second value applies to the left and right. If only three values are specified, the first value applies to the top, the second to the left and right, and the third to the bottom.

More information on CSS padding can be found here.

You can add a video by using the HTML <video> element. The <video> element requires a few attributes, such as src and controls, to properly display the video. The src attribute takes the URL of the video file, and the controls attribute will enable the HTML video player controls. An example would look like this:

<video src="example_video.mp4" width="320" height="240" controls></video>

The best way to show a video in CSS is to use the video element. The video element allows you to embed videos into an HTML page and manipulate them using CSS. You can set the size, adjust margins, or even style the video player with CSS.

Example:

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<video width="320" height="240" controls>
   <source src="movie.mp4" type="video/mp4">
</video>

For more information, please refer to this tutorial: How to embed Video using HTML5.