html5点击返回键怎样不让它返回上一页？

You can prevent the default back button behavior (navigating to the previous page) in HTML5 using JavaScript. Here's how you can do it, along with explanations and different approaches depending on what you want to achieve:

1. Using history.pushState() (Recommended for Single Page Applications):

This method is generally preferred for modern web apps, especially those using frameworks like React, Angular, or Vue.js. It modifies the browser history without actually reloading the page.

// On page load or when you want to disable the back button
window.history.pushState(null, '', window.location.href);

window.addEventListener('popstate', function(event) {
  // This function will be called when the back button is clicked
  // Prevent the default behavior
  event.preventDefault();

  // Add your custom logic here, e.g., show a confirmation dialog
  if (confirm("Are you sure you want to leave this page?")) {
    // Allow going back if the user confirms
    window.history.back();
  } else {
    // Push the current state again to prevent going back
    window.history.pushState(null, '', window.location.href);
  }
});

Explanation:

• history.pushState(null, '', window.location.href): This line adds the current URL to the browser history. The first argument (null) is a state object (you can store data here if needed), the second is the title (not used by most browsers), and the third is the URL.
• popstate event: This event is triggered when the active history entry changes, such as when the back or forward button is clicked.
• event.preventDefault(): This crucial line stops the default back button action.
• Custom Logic: Inside the popstate event listener, you can implement your desired behavior, like showing a confirmation dialog, navigating to a different section of your app, or simply doing nothing.

2. Overriding onbeforeunload (Less Recommended - Use with Caution):

This method can be used to display a confirmation dialog before the user leaves the page, but it's generally less recommended because it can be disruptive and is often misused. It also affects other ways of leaving the page, like closing the tab or navigating to a different URL.

window.onbeforeunload = function(event) {
  // This function will be called before the user leaves the page
  return "Are you sure you want to leave this page?"; // This message will be shown in the confirmation dialog
};

Explanation:

• onbeforeunload: This event is triggered before the page is unloaded.
• Returning a string: Returning a non-empty string from the onbeforeunload handler will cause the browser to display a confirmation dialog with the provided message. The user can choose to stay on the page or leave.

Important Considerations:

• User Experience: Be mindful of the user experience. Blocking the back button entirely can be frustrating. Consider providing clear feedback and alternative navigation options within your application.
• Mobile Browsers: Mobile browser behavior can vary. Test your implementation thoroughly on different devices and browsers.
• Security: You cannot completely prevent a determined user from navigating back using browser developer tools or other methods. Don't rely on this for security-sensitive functionality.

Choose the approach that best suits your needs. The history.pushState() method is generally preferred for its flexibility and better user experience in single-page applications. Use onbeforeunload with extreme caution and only when absolutely necessary. Remember to prioritize a smooth and intuitive user experience.