How do I message from background to my content script?

background.tsx

chrome.webNavigation.onCompleted.addListener(async(details) => {
    if(details.frameType == "outermost_frame"){
        console.info("The user has loaded my favorite website!");
        console.log(details)
        const tabId = details.tabId
        chrome.tabs.sendMessage(tabId, {message: "Message from background script"}, function (response) {
            if (chrome.runtime.lastError) {
                console.error(chrome.runtime.lastError);
            } else {
                console.log('Message sent to content script:');
            }
        });
    }
}, filter);

chrome.webNavigation.onCompleted.addListener(async(details) => {
    if(details.frameType == "outermost_frame"){
        console.info("The user has loaded my favorite website!");
        console.log(details)
        const tabId = details.tabId
        chrome.tabs.sendMessage(tabId, {message: "Message from background script"}, function (response) {
            if (chrome.runtime.lastError) {
                console.error(chrome.runtime.lastError);
            } else {
                console.log('Message sent to content script:');
            }
        });
    }
}, filter);

content.tsx

const handleMessage = (message, sender, sendResponse) => {
    console.log('Message received in       content.jsx:', message);
    sendResponse({message: "Response from content.jsx"})
}
React.useEffect(() => {
    console.log('content is loaded')
    chrome.runtime.onMessage.addListener(handleMessage)
    return () => {
      chrome.runtime.onMessage.removeListener(handleMessage);
    };
  }, [])

const handleMessage = (message, sender, sendResponse) => {
    console.log('Message received in       content.jsx:', message);
    sendResponse({message: "Response from content.jsx"})
}
React.useEffect(() => {
    console.log('content is loaded')
    chrome.runtime.onMessage.addListener(handleMessage)
    return () => {
      chrome.runtime.onMessage.removeListener(handleMessage);
    };
  }, [])

I want to send the tab details from my background to the content script. Any help is really appreciated. I'm so tired of trying to do this.

12 Replies

AB7zz•13mo ago

ive seen docs on how to send feom content to background. But Id really like it if someone helped me with background to content

filthytone•13mo ago

https://docs.plasmo.com/framework/messaging

Plasmo Docs

Messaging API – Plasmo

The Plasmo messaging API is a powerful tool for sending real-time messages between different parts of your extension.

filthytone•13mo ago

look at Ports

AB7zz•13mo ago

@filthytone I'm trying to do as it says in the docs for ports. I'm facing this error when using const mailPort = usePort("mail"). It says

Argument of type 'string' is not assignable to parameter of type 'never'.

Argument of type 'string' is not assignable to parameter of type 'never'.

with a red underline below "mail". So when I Ctrl+left clicked usePort and when inside node_modules/@plasmohq/messaging/dist/hook.d.ts and checked the definition for usePort, it looks like this

declare const usePort: PlasmoMessaging.PortHook;
/**
 * TODO: Perhaps add a way to detect if this hook is being used inside CS?
 */

declare const usePort: PlasmoMessaging.PortHook;
/**
 * TODO: Perhaps add a way to detect if this hook is being used inside CS?
 */

Thats it? But on github it looks completely different.

export const usePort: PlasmoMessaging.PortHook = (name) => {
  const portRef = useRef<chrome.runtime.Port>()
  const reconnectRef = useRef(0)
  const [data, setData] = useState()

  useEffect(() => {
    if (!name) {
      return null
    }

    const { port, disconnect } = portListen(
      name,
      (msg) => {
        setData(msg)
      },
      () => {
        reconnectRef.current = reconnectRef.current + 1
      }
    )

    portRef.current = port
    return disconnect
  }, [
    name,
    reconnectRef.current // This is needed to force a new port ref
  ])

  return {
    data,
    send: (body) => {
      portRef.current.postMessage({
        name,
        body
      })
    },
    listen: (handler) => portListen(name, handler)
  }
}
/**
 * TODO: Perhaps add a way to detect if this hook is being used inside CS?
 */

export const usePort: PlasmoMessaging.PortHook = (name) => {
  const portRef = useRef<chrome.runtime.Port>()
  const reconnectRef = useRef(0)
  const [data, setData] = useState()

  useEffect(() => {
    if (!name) {
      return null
    }

    const { port, disconnect } = portListen(
      name,
      (msg) => {
        setData(msg)
      },
      () => {
        reconnectRef.current = reconnectRef.current + 1
      }
    )

    portRef.current = port
    return disconnect
  }, [
    name,
    reconnectRef.current // This is needed to force a new port ref
  ])

  return {
    data,
    send: (body) => {
      portRef.current.postMessage({
        name,
        body
      })
    },
    listen: (handler) => portListen(name, handler)
  }
}
/**
 * TODO: Perhaps add a way to detect if this hook is being used inside CS?
 */

Please help me solve this. I'd really appreciate it

filthytone•13mo ago

it's because you also need to define background/ports/mail.ts and then do a dev build which will generate the types for that mail port once you have that, you'll see the typescript never error go away

AB7zz•13mo ago

@filthytone yo dude. Thanks a lot!! That solved my error. I thought I had put it in

background/ports/mail.ts

background/ports/mail.ts

but instead I did

backround/ports/mail.ts

backround/ports/mail.ts

and I ran the pnpm build and loading the dev build works perfectly fine now. I'm receiving the message on both sides. So relieved!

YAGPDB.xyz•13mo ago

Gave +1 Rep to @filthytone

Asif•9mo ago

hello @AB7zz can you share how you solve that? @AB7zz sure. Native messaging is not working here. Plasmo messaging system is working fine. If i use this in my content script or anywhere

  chrome.runtime.onMessage.addListener(function (message) {
    console.log("details message", message)
  })

I found this error Uncaught (in promise) Error: Could not establish connection. Receiving end does not exist. Can you help me to use native messaging system

banshee•5mo ago

When I was seeing that erorr, I just removed my extension and restarted Chrome. Added the extension back and everything worked fine.

Arcane•5mo ago

@banshee has reached level 1. GG!

Mesh•2mo ago

@Asif , @banshee I am also running into the same problem - very similar to the issue described here: https://discord.com/channels/946290204443025438/1268435446942273556 any guidance? @filthytone I am trying to use the messaging flow so that a content script button triggers background scripts, and depending on response the content script is updated. Would I use ports for this? I keep getting the issue referenced here: https://discord.com/channels/946290204443025438/1268435446942273556

filthytone•2d ago

it depends on how long the content script will wait for some response from the backend .. if it's a small amount of time, you can probably just send a message to the background and await its response ... but if you need to do something more long running then you could use ports ... as for what issue you're getting, can you be more specific?

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How do I message from background to my content script?