写一个 document.querySelector 的逆方法

function querySelectorAllReverse(selector) {
  const elements = document.querySelectorAll(selector);
  return Array.from(elements).reverse();
}


// Example usage:

// Assuming your HTML contains:
// <div class="my-element">1</div>
// <div class="my-element">2</div>
// <div class="my-element">3</div>

const reversedElements = querySelectorAllReverse('.my-element');

reversedElements.forEach(element => {
  console.log(element.textContent); // Output: 3, 2, 1 (reversed order)
});


// More robust version handling invalid selectors:

function querySelectorAllReverseRobust(selector) {
  try {
    const elements = document.querySelectorAll(selector);
    return Array.from(elements).reverse();
  } catch (error) {
    console.error("Invalid selector:", selector, error);
    return []; // Return an empty array to avoid further errors
  }
}

Explanation:

1. querySelectorAll(selector): This standard JavaScript method selects all elements in the document that match the given CSS selector. It returns a NodeList.

2. Array.from(elements): NodeList isn't a true array, so we convert it to an array using Array.from(). This allows us to use array methods like reverse().

3. reverse(): This array method reverses the order of elements in the array in place.

4. Robust Version: The querySelectorAllReverseRobust function includes error handling. If the provided selector is invalid, querySelectorAll will throw an error. The try...catch block catches this error, logs it to the console, and returns an empty array to prevent the script from crashing.

Why not a true "inverse" querySelector?

A true inverse of querySelector (finding the selector for a given element) is significantly more complex. It would involve:

• Traversing the DOM tree up to the root.
• Considering all possible CSS selectors (tags, classes, IDs, attributes, combinations, pseudo-selectors, etc.).
• Potentially generating multiple valid selectors for the same element.
• Dealing with dynamic content and changes in the DOM.

While libraries exist to generate selectors for elements (often used in testing), they are not a direct inverse and often produce overly specific selectors. The provided querySelectorAllReverse function addresses the more common need of simply reversing the order of a selected set of elements.