Chrome Extension content_script at both document_start and document_end

Question

Good day to everyone, as you can see I'm pretty new at Chrome extensions.

Can you run a script from content_scripts before and after the the DOM or page fully loads?

Like:

"content_scripts": [ {
    "matches": ["<all_url>"],
    "js": ["content.js"],
    "all_frames": true,
    "run_at": "document_start",
    "run_at": "document_end"
} ]

Or something like:

 "content_scripts": [ {
    "matches": ["<all_url>"],
    "js": ["content1.js"],
    "all_frames": true,
    "run_at": "document_start"
} ],
"content_scripts": [ {
    "matches": ["<all_url>"],
    "js": ["content2.js"],
    "all_frames": true,
    "run_at": "document_end"
} ]

i want it to be before the page and after, any method will be fine. — Francis ask question, Mar 20 '19 at 07:52
An important note: there is no general "all DOM is loaded now" state you can detect if the page dynamically creates more DOM (e.g. infinite scroll). This needs to be dealt with [different techniques](https://stackoverflow.com/questions/2844565/is-there-a-javascript-jquery-dom-change-listener). `document_end` (or `document_idle`) guarantees only that all static DOM has been parsed. — Xan, Mar 20 '19 at 10:38
Xan, well for that case I run a script that run indefinitely. Well my only concern was to run a two different script before and after the page loaded. — Francis ask question, Mar 21 '19 at 05:35

Iván Nokonoko · Accepted Answer · 2020-12-08T10:10:57.993

2

You can have only one content_scripts entry, so it would be like:

"content_scripts": [{
    "matches": ["<all_urls>"],
    "js": ["content1.js"],
    "all_frames": true,
    "run_at": "document_start"
  },{
    "matches": ["<all_urls>"],
    "js": ["content2.js"],
    "all_frames": true,
    "run_at": "document_end"
}]

With this setting, content1.js would run at the beginning and content2.js at the end.

edited Dec 08 '20 at 10:10

answered Mar 20 '19 at 08:14

Iván Nokonoko

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score 1 · Answer 2 · answered Mar 20 '19 at 08:15

You are going in the right direction: You can use the run_at property, but your manifest needs to look something like this:

"content_scripts": [
{
    "matches": ["<all_url>"],
    "js": ["content1.js"],
    "all_frames": true,
    "run_at": "document_start"
},
{
    "matches": ["<all_url>"],
    "js": ["content2.js"],
    "all_frames": true,
    "run_at": "document_end"
}]

It should be an array of objects defining all content scripts instead to declaring the content_script property twice.

If you are using jQuery you can also use $(document).ready() like this:

const func1 = params => {
    // Stuff that will happen as soon as it can
};

$(document).ready(() => {
    // stuff that will happen when DOM is ready
});

If you are not using jQuery you can just do a quick google search to find alternatives for $(document).ready in vanilla js.

Other solution you can use it to inject content script programmatically from background script using chrome.tabs.executeScript() docs.

This is also correct, Thanks, cannot vote up yet, and the other guy answered earlier. — Francis ask question, Mar 20 '19 at 08:25
`func1` code will not run unless you explicitly call it, like `func1()` — Iván Nokonoko, Mar 20 '19 at 15:56

Chrome Extension content_script at both document_start and document_end

2 Answers2