Overview of the Issue

The question is about an error that occurs when trying to send a message from the background.js script to the content.js script in a Chrome extension using the chrome.tabs.sendMessage() method. The error message is: "TypeError: Error in invocation of tabs.sendMessage(integer tabId, any message, optional object options, optional function responseCallback): No matching signature."

Code Provided

The code snippets provided are:

• background.js: This script listens for the browser action (extension icon) click event, gets the active tab, and tries to send a message with the string "run" to the content script.
• content.js: This script listens for incoming messages from the background script and calls a function named "view()" when a message is received.

Solution and Explanation

The accepted answer suggests modifying the line in background.js where the message is sent:

chrome.tabs.sendMessage(CurrTab, 'run');

to:

chrome.tabs.sendMessage(CurrTab.id, 'run');

The reason for this change is that the chrome.tabs.sendMessage() method expects the first argument to be the tabId, which is an integer representing the tab to which the message should be sent. In the original code, CurrTab was passed directly, which is an object containing tab information, not the tabId itself.

Importance of matches in manifest.json

The accepted answer also mentions the importance of specifying the URL of the website where the content script needs to be injected in the content_scripts/matches section of the manifest.json file. This ensures that the content script is only loaded on the intended pages, which can improve performance and security.

Summary of Steps

To summarize the steps to fix the issue:

Importance of matches Keyword

The "matches" keyword is crucial in the context of Chrome extensions because it specifies the URLs or URL patterns on which the content scripts should be injected. By properly configuring the "matches" in the manifest.json file, you can ensure that your content scripts are loaded only on the intended web pages, improving the performance and security of your extension.

Here are some key points regarding the "matches" keyword:

• The "matches" keyword is used within the "content_scripts" section of the manifest.json file.
• It accepts an array of strings, where each string represents a URL pattern.
• URL patterns can use wildcards (*) to match multiple URLs.
• For example, "*://www.example.com/*" would match all pages on the www.example.com domain.
• By carefully specifying the "matches" patterns, you can ensure that your content scripts are only injected on the relevant pages, reducing the risk of conflicts or performance issues.

Importance of manifest.json

The manifest.json file is a crucial component of any Chrome extension, as it provides metadata and configuration settings for the extension. Some key aspects of the manifest.json file include:

• Specifying the permissions required by the extension (e.g., accessing specific URLs, host permissions, etc.).
• Defining the background scripts, content scripts, and other components of the extension.
• Configuring the user interface elements, such as browser action buttons or context menu items.
• Providing metadata like the extension name, version, and description.

Properly configuring the manifest.json file is essential for ensuring that your Chrome extension functions as intended and adheres to best practices for performance, security, and user experience.