ChromeDevSnippet.md

Install Systemback -also consider w/Debian version

https://github.com/fconidi/systemback-install_pack-1.9.3
with source forge

Run and Save a js snippet to modify DOM in Chrome Dev Tools

console.log('Hello, Snippets!');  
document.body.innerHTML = '';  
var p = document.createElement('p');  
p.textContent = 'Hello, Snippets!';    
document.body.appendChild(p);  

All DOM document elements

document.documentElement.style.fontSize="60%";

Or loop through certain element

{
  var x = document.body;  
  var y = x.getElementsByTagName("h1");  
  var i;  
  for (i = 0; i < y.length; i++) {  
    y[i].style.fontSize="80%";  
  }
}