document.getelementbyid(...) is null
When you run the above script , you will the get the error:
TypeError: document.getElementById(...) is null
If you change the order of the script after the element so that it's defined when getElementById is called.Example:
Alternatively, you can check the null to solve this issue. The standard way to catch null and undefined simultaneously is this:
In cases where you're not using TypeScript, implementing guard clauses to verify whether objects are undefined before using them is a good practice. This helps prevent your code from encountering runtime errors by ensuring that data is valid before proceeding with any operations. By being proactive in handling potential null or undefined scenarios, you contribute to more stable and error-resistant code.
When the browser encounters a script in the HTML, it halts parsing to execute the script immediately. This can temporarily block the building of the Document Object Model (DOM). The DOMContentLoaded event typically occurs after these blocking scripts have executed, ensuring that the DOM is ready for manipulation.
The async and defer attributes in external script tags provide ways to optimize this behavior. With async, the script is executed asynchronously without blocking the HTML parsing. With defer, the script is executed after the HTML parsing is complete, just before the DOMContentLoaded event. These attributes help improve page loading performance and user experience by allowing content to be displayed while scripts load in the background.