Changing button text onclick in javascript

Question

I would like to enable a dark mode feature on my website by using a toggle button. I already got dark mode to work now I would like to have the button say Turn on dark mode when it is off and then Turn off dark mode when it is on.

function myFunction() {
   var element = document.body;
   element.classList.toggle("dark-mode");
}

body {
	margin: 0;
	font-family: Arial, Helvetica, sans-serif;
	background-color: white;
	color: black;
}

.dark-mode {
	background-color: black;
	color: white;
}

<button onclick="myFunction()">Turn on dark mode</button>

Answer 1

function myFunction() {
   var element = document.body;
   var btn = document.getElementById("modeSwitcher");
   element.classList.toggle("dark-mode");
   if(element.classList.contains("dark-mode"))
    btn.innerHTML= "Turn off dark mode";
   else 
    btn.innerHTML= "Turn on dark mode";
}

body {
	margin: 0;
	font-family: Arial, Helvetica, sans-serif;
	background-color: white;
	color: black;
}

.dark-mode {
	background-color: black;
	color: white;
}

<button onclick="myFunction()" id="modeSwitcher">Turn on dark mode</button>