Do you mean smth like this?
function handleButtonClicked(type) {
if (type === 'main') {
const mainElement = document.getElementById('subele1')
mainElement.innerHTML += '!'
}
if (type === 'sub') {
const mainElement = document.getElementById('subele2')
mainElement.innerHTML += '?'
}
}
<div id="mainWindow">
<div id="subele1">main Window!</div>
</div>
<div id="subWindow">
<div id="subele2">sub Window?</div>
</div>
<button id='main' onclick={handleButtonClicked('main')}>main</button>
<button id='sub' onclick={handleButtonClicked('sub')}>sub</button>
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