JS功能在chrome控制台上有效，但从插件加载时无效

Question

So I have a webpage with a function applaud. When I call it from the console, I get the normal return:

applaud(3004,1935);
undefined

However, if I use CTG plugins (simple plugin to run a js script), with that code

applaud(3004,1935);

I get the following error in console:

3VM5444:1 Uncaught ReferenceError: applaud is not defined
    at <anonymous>:1:1
(anonymous) @ VM5444:1

and function isn't working.

Do you know how I can use it?

Thanks.

Answer 1

I know this is a bit outdated, but I can answer this. (I made the extension in question.)

Chrome Extensions by default insert scripts into a webpage in a different context than the rest of the page. This is for security reasons. If you'd like to run code in the context of the webpage, you'd need to use a little workaround.

In the script that the Chrome Extension injects, have that inject a <script> tag into the body of the page. Then that script will be loaded and be able to execute the functions like you can in the console.

Here's a demo of code that can do what I'm talking about:

//Create a new script element.
var script = document.createElement("script");

//Get the function you want to inject as a string and add it to the script.
script.innerHTML = injection.toString();

//Add a call to that injection function so it'll automatically execute once it's injected.
script.innerHTML += "injection();";

//Inject that newly created script into the body of the page.
document.body.appendChild(script);

//The contents of this script will be run inside the same context as the webpage.
function injection(){
    applaud(3004, 1935);
}