Twitter公式の画像一覧でツイートの内容を一緒に表示されるようにするやつ

manifest.json

{
  "name" : "tweet-disp",
  "version" : "0.0.1",
  "manifest_version" : 2,
  "description" : "disp tweet in media. in 2017/6/25",                                                                                                                                                             
  "content_scripts" : [ 
    {   
      "matches" : [ 
        "https://twitter.com/*"
      ],  
      "js" : ["script.js"]
    }   
  ]
}

script.js

(function(){
  "use strict"
  const elem = ".GalleryTweet .content>*"
  const gElem = ".GalleryTweet"
  const fit = ".media-image"
  
  // .GalleryTweet DOM
  let gallery = document.querySelector(gElem)

  let command = function(){                                                                                                                                                                                        
    let items = document.querySelectorAll(elem)
    let size = document.querySelector(fit)
    for( let v of items ){
      //display : none -> display : block
      v.style.display = "block"
    }
    size.style.margin = "0"
  };  
  
  // .GalleryTweetを監視し,変更されたらcommandを実行
  let mo = new MutationObserver(command)
  
  // 子ノードを監視対象にする
  const options = {childList : true}
  //監視開始
  mo.observe(gallery,options);

}())