The best way to load external JavaScript | NCZOnline
Not too long ago, I wrote about loading JavaScript without blocking by creating a dynamic <script> tag. When <script> tags are in the flow of an HTML document, the browser must stop rendering and wait for the script file to download and execute before continuing (example). Creating a new <script> tag via JavaScript avoids this issue because it’s out of the flow of the document, so the script file is downloaded and executed without waiting. The result: dynamically loading JavaScript files allows your page to render faster and therefore improve perceived performance.
