can we use js variable name as class name in html

I want to concatinate class name with variable count which keep getting updated after each button click, for which I am getting error as “citysName is null”. can anyone suggest

button.addEventListener('click', resp => {
    count = count +1;
    var card = document.createElement('card');
    card.innerHTML = `
                <img src="..." class="card-img-top" alt="...">
                <div class="card-body">
                  **<h5 class="card_title" + count></h5>
                  <h6 class="temp" + count></h6>
                  <p class="card-text" + count></p>**
                  <a href="#" class="btn-primary"></a>
                </div>
    `;
    card.className = 'card';
    var content = document.getElementById('id1');
    content.appendChild(card);
    **var citysName = document.querySelector('.card_title'+count);
    var description = document.querySelector('.card-text'+count);
    var temp = document.querySelector('.temp'+count);**
    fetch('https://api.openweathermap.org/data/2.5/weather?q='+inputVal.value+'&appid=a5599c020b0d897cbc8b52d547289acc')
    .then(post => post.json())
    .then(data => {
        var cityName = data['name'];
        var temper = data['main']['temp'];
        var descrip = data['weather'][0]['description'];

        let ctemp = Math.round(temper-273);
        citysName.innerHTML = cityName;
        temp.innerHTML = ctemp + "°C";
        description.innerHTML = descrip;
    })
})