tokisakiyuu/README.md

## README.md

      
    Raw
  

              README.md
            
          
    FORM: https://stackoverflow.com/a/69361046/11537100

  
## inject.js
const nullthrows = (v) => {
    if (v == null) throw new Error("it's a null");
    return v;
}

function injectCode(src) {
    const script = document.createElement('script');
    // This is why it works!
    script.src = src;
    script.onload = function() {
        console.log("script injected");
        this.remove();
    };

    // This script runs before the <head> element is created,
    // so we add the script to <html> instead.
    nullthrows(document.head || document.documentElement).appendChild(script);
}


injectCode(chrome.runtime.getURL('/myscript.js'));

## manifest.json
{
  "name": "example",
  "version": "1.0",
  "description": "example extension",
  "manifest_version": 3,
  "content_scripts": [
    {
      "matches": ["https://*/*"],
      "run_at": "document_start",
      "js": ["inject.js"]
    }
  ],
  "web_accessible_resources": [
    {
      "resources": [ "myscript.js" ],
      "matches": [ "https://*/*" ]
    }
  ]
}

## myscript.js
window.variableInMainContext = "hi"
	const nullthrows = (v) => {
	if (v == null) throw new Error("it's a null");
	return v;
	}

	function injectCode(src) {
	const script = document.createElement('script');
	// This is why it works!
	script.src = src;
	script.onload = function() {
	console.log("script injected");
	this.remove();
	};

	// This script runs before the <head> element is created,
	// so we add the script to <html> instead.
	nullthrows(document.head \|\| document.documentElement).appendChild(script);
	}


	injectCode(chrome.runtime.getURL('/myscript.js'));
	{
	"name": "example",
	"version": "1.0",
	"description": "example extension",
	"manifest_version": 3,
	"content_scripts": [
	{
	"matches": ["https:///"],
	"run_at": "document_start",
	"js": ["inject.js"]
	}
	],
	"web_accessible_resources": [
	{
	"resources": [ "myscript.js" ],
	"matches": [ "https:///" ]
	}
	]
	}