将contentcript连接到扩展

Question

我正在使用contentcript进行扩展。它应该更改DOM元素的段落，但它不起作用。 这是我的.json文件

    {
  "name": "MyExtension",
  "version": "0.5",
  "description": "Moja prva extenzija!",
  "permissions": ["storage",
  "activeTab"],
  "background": {
    "scripts": ["background.js"],
    "persistent": false
  },
  "content_scripts": [
  {
    "matches": ["<all_urls>"],
    "run_at": "document_idle",
    "js": ["contentScript.js"]
  }
],
"browser_action":{
  "default_icon":"h3.png",
  "default_popup":"popup.html"
},
  "manifest_version": 2
}

这是我的contentScript.js：

document.getElementById("click").onclick= funt; // "click" is button of extension

function funt() {
document.getElementById("demo").innerHTML="Hello"; //demo is DOM element
}