JavaScript - Utilizing appendChild as soon as an element becomes available

Question

JavaScript - Utilizing appendChild as soon as an element becomes available

I'm encountering an issue with my Chrome Extension where I am unable to detect some of the elements that I need to select within a page.

var innerChat = document.querySelector('.chat-list');

My goal is to appendChild to this element, but the problem is that the script moves on to edit it before the element even exists.

innerChat.appendChild(emoteMenuWrap);

This leads to the error:

Uncaught TypeError: Cannot read property 'appendChild' of null

What would be the best approach to resolve this issue?

javascript google-chrome-extension

Answer 1

Answer №1

One potential solution could be to utilize a mutation observer. In cases where this is not available, an alternative approach using getElementsByClassName may work since it returns a live list:

var chatContainer = document.getElementsByClassName("chat-list");

You can incorporate the following code snippet into your existing script:

function process(){
   if(!chatContainer.length){
       requestAnimationFrame(process);
   } else {
       chatContainer[0].appendChild(emoteMenuWrap);
   }
}
requestAnimationFrame(process);

Answer 2

One potential solution could be to utilize a mutation observer. In cases where this is not available, an alternative approach using getElementsByClassName may work since it returns a live list:

var chatContainer = document.getElementsByClassName("chat-list");

You can incorporate the following code snippet into your existing script:

function process(){
   if(!chatContainer.length){
       requestAnimationFrame(process);
   } else {
       chatContainer[0].appendChild(emoteMenuWrap);
   }
}
requestAnimationFrame(process);

Answer 3

Answer №2

To achieve this, utilize a MutationObserver in your code.

If you have an element called innerChat that is nested within another element named chatDiv, ensure that chatDiv is present on the webpage while innerChat may not be initially:

const observer = new MutationObserver(callbackFunction)
const config = { subtree: true };
observer.observe(chatDiv, config);

The callback function assigned to the observer will run whenever there are changes detected within chatDiv, for example adding innerChat to it.

Within the callback function, you can perform any required actions based on the observed changes.

It's important to select the parent container carefully to avoid triggering the event multiple times due to unrelated changes happening inside it.

Lastly, remember to disconnect the observer once it has served its purpose:

observer.disconnect();

Note: It's recommended to observe the subtree since new elements are being added rather than altering existing ones in this scenario.

Answer 4

To achieve this, utilize a MutationObserver in your code.

If you have an element called innerChat that is nested within another element named chatDiv, ensure that chatDiv is present on the webpage while innerChat may not be initially:

const observer = new MutationObserver(callbackFunction)
const config = { subtree: true };
observer.observe(chatDiv, config);

The callback function assigned to the observer will run whenever there are changes detected within chatDiv, for example adding innerChat to it.

Within the callback function, you can perform any required actions based on the observed changes.

It's important to select the parent container carefully to avoid triggering the event multiple times due to unrelated changes happening inside it.

Lastly, remember to disconnect the observer once it has served its purpose:

observer.disconnect();

Note: It's recommended to observe the subtree since new elements are being added rather than altering existing ones in this scenario.

JavaScript - Utilizing appendChild as soon as an element becomes available

Answer №1

Answer №2

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