SOURCE

const app = document.querySelector('#app')
const test = document.querySelector('#test')

test.onclick = function(){
    app.style.display=app.style.display==='block'?'none':'block'
    const height = app.offsetHeight;
    console.log(height)
    app.style.transform= 'translateX(250px)'
}

<div id="app">
</div>
<button id="test">测试</button>

#app {
    width: 200px;
    height: 200px;
    background-color: red;
    display: none;
    transition: all 1s;
}