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How to use js code

百草Original: 2023-10-08 10:13:431721browse

js code can be embedded in HTML files inline or external files. Dynamic effects and interactive behaviors of web pages can be achieved through event processing, DOM manipulation, conditional statements, and loops. Detailed introduction: 1. Inline mode, you can embed JavaScript code directly in the "script" tag of the HTML file; 2. External file mode, you can save the JavaScript code in an independent `.js` file and pass it through "src" ” attribute to introduce it into the HTML file and so on.

How to use js code

# Use JavaScript (JS for short) code to achieve dynamic effects and interactive behaviors on web pages. The following will introduce some basic usage methods and techniques:

1. Inline method: JavaScript code can be directly embedded in the `3f1c4e4b6b16bbbd69b2ee476dc4f83a` tag of the HTML file. For example:

<!DOCTYPE html>
<html>
<head>
  <title>JavaScript Demo</title>
</head>
<body>
  <h1>JavaScript Demo</h1>
  
  <script>
    // 在这里编写JavaScript代码
    var message = "Hello, World!";
    console.log(message);
  </script>
</body>
</html>

The JavaScript code written within the `3f1c4e4b6b16bbbd69b2ee476dc4f83a` tag will be executed when the browser loads the HTML file.

2. External file method: You can save the JavaScript code in a separate `.js` file and introduce it into the HTML file through the `src` attribute. For example:

<!DOCTYPE html>
<html>
<head>
  <title>JavaScript Demo</title>
  <script src="script.js"></script>
</head>
<body>
  <h1>JavaScript Demo</h1>
</body>
</html>

In the above example, `script.js` is a separate JavaScript file that contains the code that needs to be executed.

3. Event handling: JavaScript can be used to handle user interaction events, such as clicking buttons, submitting forms, etc. This can be achieved by adding event listeners to HTML elements. For example:

<button id="myButton">Click me</button>
<script>
  var button = document.getElementById("myButton");
  button.addEventListener("click", function() {
    alert("Button clicked!");
  });
</script>

In the above example, when the user clicks the button, the JavaScript code will pop up a dialog box to display the message.

4. Manipulate DOM: JavaScript can access and modify HTML elements by manipulating the DOM (Document Object Model). You can use the `document` object to obtain elements and manipulate their content, styles, etc. For example:

<p id="myParagraph">This is a paragraph.</p>
<script>
  var paragraph = document.getElementById("myParagraph");
  paragraph.innerHTML = "This is a new paragraph.";
  paragraph.style.color = "red";
</script>

In the above example, the JavaScript code gets the paragraph element with a specific ID and modifies its content and style.

5. Conditional statements and loops: JavaScript supports conditional statements (such as `if`, `switch`) and loop statements (such as `for`, `while`) to achieve logical control and repeated execution. For example:

<script>
  var age = 18;
  
  if (age >= 18) {
    console.log("You are an adult.");
  } else {
    console.log("You are a minor.");
  }
  
  for (var i = 0; i < 5; i++) {
    console.log(i);
  }
</script>

In the above example, the JavaScript code outputs different messages depending on the age. Then, use a loop statement to output a series of numbers.

It should be noted that JavaScript is an interpreted language, and the code will be parsed and executed line by line when running in the browser. Therefore, when writing code, you need to pay attention to the correctness of the grammar and the logic of the code.

In summary, JavaScript code can be embedded in an HTML file inline or in an external file. Dynamic effects and interactive behaviors of web pages can be achieved through event processing, DOM manipulation, conditional statements, and loops. When writing JavaScript code, you need to pay attention to the correctness of the syntax and the logic of the code to achieve the desired effect.

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