Google chrome extension chrome扩展中的内容脚本

我必须通过chrome扩展在谷歌搜索页面中添加div 我的inject.js文件如下：

var body=document.getElementById("search");

//creates bar and creates bar removal function
var bar = document.createElement("DIV");
function removeBar(){
  bar.remove();
}

//styles bar
var ds = bar.style;
ds.position = "fixed";
ds.width = "512px";
ds.height = "33px";
ds.background = "rgba(0,0,0,0.86)";
ds.zIndex = "9999999999999";

//creates X button and makes it so clicking it runs the removeBar() function
var x = document.createElement("BUTTON");
x.onclick = removeBar;
bar.appendChild(x);

//styles button
var xs = x.style;
xs.background = "black";
xs.borderColor = "black";
xs.color = "rgba(255,255,255,.86)";
xs.position = "fixed";
xs.left = "100%";
xs.marginTop = "5px";
xs.marginLeft = "-29px"

//puts X in button
var xtext = document.createTextNode("X");
x.appendChild(xtext);

//puts bar in page
body.insertBefore(bar, body.children[0]);

{
  "manifest_version": 2,
  "name": "Inject script in webpage",
  "version": "2.0.1",
  "description": "inject script in webpage.",

  "icons": {
    "48" : "sample-48.png",
    "128" : "sample-128.png"
  },
  "content_scripts": [
    {
      "matches": ["https://www.google.com.pk/*"],
      "js" : ["inject.js"],
      "all_frames": true
    }
  ]
}

我的manifest.json如下所示：

var body=document.getElementById("search");

//creates bar and creates bar removal function
var bar = document.createElement("DIV");
function removeBar(){
  bar.remove();
}

//styles bar
var ds = bar.style;
ds.position = "fixed";
ds.width = "512px";
ds.height = "33px";
ds.background = "rgba(0,0,0,0.86)";
ds.zIndex = "9999999999999";

//creates X button and makes it so clicking it runs the removeBar() function
var x = document.createElement("BUTTON");
x.onclick = removeBar;
bar.appendChild(x);

//styles button
var xs = x.style;
xs.background = "black";
xs.borderColor = "black";
xs.color = "rgba(255,255,255,.86)";
xs.position = "fixed";
xs.left = "100%";
xs.marginTop = "5px";
xs.marginLeft = "-29px"

//puts X in button
var xtext = document.createTextNode("X");
x.appendChild(xtext);

//puts bar in page
body.insertBefore(bar, body.children[0]);

{
  "manifest_version": 2,
  "name": "Inject script in webpage",
  "version": "2.0.1",
  "description": "inject script in webpage.",

  "icons": {
    "48" : "sample-48.png",
    "128" : "sample-128.png"
  },
  "content_scripts": [
    {
      "matches": ["https://www.google.com.pk/*"],
      "js" : ["inject.js"],
      "all_frames": true
    }
  ]
}

---

但当我加载GoogleSERP页面时，错误消息显示有点像不能调用null的insertBefore属性，似乎变量体未定义。通过检查google页面的元素，我检查了带有ID搜索的DIV是否存在，如果我做错了，那么plzz让我知道我是chrome扩展开发的新手

问题可能在这里：

var body=document.getElementById("search");

body变量为null-可能是因为您要查找的id不存在。尝试寻找我使用的其他id gbqfb。但与其在这里给你答案，你真正应该做的是学会使用Chrome的内置调试器来找出代码不工作的原因。看看这段youtube视频：

---

@齐格曼德尔？默认设置是在加载DOM后运行，OP不会改变这一点。对不起，你是对的。问题可能是使用了名为body的变量，请将其重命名为其他变量，因为下面的其他引用似乎引用了document.body