title: Chrome Extension - Get DOM content
body: <p>I'm trying to access the activeTab DOM content from my popup. Here is my manifest:</p>
  
  <pre><code>{
    "manifest_version": 2,
  
    "name": "Test",
    "description": "Test script",
    "version": "0.1",
  
    "permissions": [
      "activeTab",
      "https://api.domain.com/"
    ],
  
    "background": {
      "scripts": ["background.js"],
      "persistent": false
    },
    "content_security_policy": "script-src 'self' 'unsafe-eval'; object-src 'self'",
  
    "browser_action": {
      "default_icon": "icon.png",
      "default_title": "Chrome Extension test",
      "default_popup": "index.html"
    }
  }
  </code></pre>
  
  <p>I'm really confused whether background scripts (event pages with persistence: false) or content_scripts are the way to go. I've read all the documentation and other SO posts and it still makes no sense to me.</p>
  
  <p>Can someone explain why I might use one over the other.</p>
  
  <p>Here is the background.js that I've been trying:</p>
  
  <pre><code>chrome.extension.onMessage.addListener(
    function(request, sender, sendResponse) {
      // LOG THE CONTENTS HERE
      console.log(request.content);
    }
  );
  </code></pre>
  
  <p>And I'm just executing this from the popup console:</p>
  
  <pre><code>chrome.tabs.getSelected(null, function(tab) {
    chrome.tabs.sendMessage(tab.id, { }, function(response) {
      console.log(response);
    });
  });
  </code></pre>
  
  <p>I'm getting:</p>
  
  <pre><code>Port: Could not establish connection. Receiving end does not exist. 
  </code></pre>
  
  <p><strong>UPDATE:</strong></p>
  
  <pre><code>{
    "manifest_version": 2,
  
    "name": "test",
    "description": "test",
    "version": "0.1",
  
    "permissions": [
      "tabs",
      "activeTab",
      "https://api.domain.com/"
    ],
  
    "content_scripts": [
      {
        "matches": ["&lt;all_urls&gt;"],
        "js": ["content.js"]
      }
    ],
  
    "content_security_policy": "script-src 'self' 'unsafe-eval'; object-src 'self'",
  
    "browser_action": {
      "default_icon": "icon.png",
      "default_title": "Test",
      "default_popup": "index.html"
    }
  }
  </code></pre>
  
  <p>content.js</p>
  
  <pre><code>chrome.extension.onMessage.addListener(
    function(request, sender, sendResponse) {
      if (request.text &amp;&amp; (request.text == "getDOM")) {
        sendResponse({ dom: document.body.innerHTML });
      }
    }
  );
  </code></pre>
  
  <p>popup.html</p>
  
  <pre><code>chrome.tabs.getSelected(null, function(tab) {
    chrome.tabs.sendMessage(tab.id, { action: "getDOM" }, function(response) {
      console.log(response);
    });
  });
  </code></pre>
  
  <p>When I run it, I still get the same error:</p>
  
  <pre><code>undefined
  Port: Could not establish connection. Receiving end does not exist. lastError:30
  undefined
  </code></pre>