My div id is ," my_age" and inner html property is "45"

So I want to change inner html as '56'

What are the java script code to write for tamper monkey....pls help me

I think property can mean a lot of things, so you should be more specific.

document.querySelector("#my_age , .my_age").innerHTML = '56';

You might actually be talking about innerText instead of innerHTML.

To briefly explain the differences, here's some code:

var div = document.createElement("div"); // <div></div>

div.innerText = "<h1>Hello</h1>"; // <div>"<h1>Hello</h1>"</div>
div.innerHTML = "<h1>Hello</h1>"; // <div><h1>"Hello"</h1></div>

And here's the result of the code:

<h1>Hello</h1>

Hello

I think the above has already answered your question. But try the method that is described on the casinoshunter. It seems to me that he will be more working in the end.

var html = document.getElementsByTagName('html')[0];
// do something in html.TAG_NAME
html.innerHTML = html.innerHTML;