Chrome extension set to `run_at` `document_start` is running too fast?

后端未结

关注

 2  1494

EDIT: Something was wrong with my Chrome browser and creating a conflict with my script, a full reinstall eliminated whatever the problem source was. If I happen to find out

相关标签:

2条回答

清酒与你

2020-12-08 22:50
Chrome extension Content scripts (run from a manifest.json) that are run at document_start, do fire before document.readyStateDoc has reached interactive -- which is the earliest you want to start messing with most page elements.

However, you can inject most <script> nodes right away if you wish. Just not to document.head or document.body because they don't exist yet.
Append to documentElement instead. For example:
```
var s = document.createElement ("script");
s.src = "http://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js";
s.async = false;
document.documentElement.appendChild (s);
```
Or
```
var s = document.createElement ("script");
s.src = chrome.extension.getURL ("MyPwnCode.js");
s.async = false;
document.documentElement.appendChild (s);
```
If you are adding or modifying other DOM elements, in a script running at document_start, wait until the DOMContentLoaded event like so:
```
document.addEventListener('DOMContentLoaded', fireContentLoadedEvent, false);

function fireContentLoadedEvent () {
    console.log ("DOMContentLoaded");
    // PUT YOUR CODE HERE.
    //document.body.textContent = "Changed this!";
}
```
0 讨论(0)
发布评论:

提交评论
- 加载中...
悲&欢浪女

2020-12-08 23:08
Your problem is that, when using "run_at": "document_start", the only element that is granted to exist in the DOM is the <html> element. If you want to avoid errors relative to page load, like trying to access some element that hasn't been created yet, you'll have to either:
- Make your script run at "document_idle" or "document_end". Although "document_end" still doesn't grant you that all the elements and resources of the page have been fully loaded (but the DOM has already been parsed), the "document_idle" keyword will give you the certainty that the DOM has been parsed and all the elements and resources have been loaded properly before your script runs.
- Or, instead, you can continue using "document_start" wrapping your code inside a "DOMContentLoaded" listener, which will make it run when the DOM has completely finished loading and parsing, similarly to "document_idle". Here's an example:
```
document.addEventListener("DOMContentLoaded", function() {
    // Run your code here...
});
```
0 讨论(0)
发布评论:

提交评论
- 加载中...