Why is Using `element.innerHTML =` a Performance Bottleneck?

Avoiding the Pitfalls of Element.innerHTML =

While convenient, using element.innerHTML = ... to append content can lead to significant performance implications. This is because each time innerHTML is set, the HTML has to be parsed, a DOM constructed, and inserted into the document.

Why is this a Problem?

Consider an element with a large amount of complex HTML content. Setting innerHTML with the = operator forces the parser to re-parse all of this content again, even though only a small portion may have changed. This excessive parsing can significantly slow down page rendering.

Alternatives to innerHTML =

To avoid these performance issues, consider using the following alternatives:

• appendChild(): Creates a new element node and appends it to the end of the specified element. This approach is much more efficient because it only inserts the new node into the existing DOM tree without the need for re-parsing.

var newElement = document.createElement('div');
newElement.innerHTML = '<div>Hello World!</div>';
elm.appendChild(newElement);

• insertBefore(): Inserts a new element node before the specified element child. Similar to appendChild(), this method only inserts the new node without re-parsing the existing content.

var newElement = document.createElement('div');
newElement.innerHTML = '<div>Hello World!</div>';
elm.insertBefore(newElement, elm.firstChild);

Browser Optimization Note:

While innerHTML = may not be optimal, it's important to note that some browsers may optimize this operation and avoid re-parsing the existing contents. However, relying on this optimization is not recommended, especially for performance-critical applications.

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