estilos js cuando se hace clic

const elem = document.getElementById('elem-id');
// Now that we got the element we needed,
// there are 3 ways that we can style it when it's clicked

// method 1: .onclick
elem.onclick = () => {
  elem.style.backgroundColor = 'red';
}

// method 2: .addEventListener
elem.addEventListener('click', function(){
  elem.style.backgroundColor = 'red'; 
})

// method 3: function
function funcName(){
  elem.style.backgroundColor = 'red';
}
// now that we declared the function we need to call it on click,
// we can use both method 1 & 2, replace the code and call the function there
// or we can call it on the html attribute 'onclick'

// <div id="elem-id" onclick="funcName"></div>
ST111