Thermomètre en javascript

 var cityTemperatures = {
    "Arles": 8,
    "Hanoi": 14,
    "Lille": 4,
    "Nancy": 1,
    "Nîmes": 8,
    "Paris": 5,
    "Rabat": 15,
    "Tokyo": 8,
    "Tunis": 13
};

function addCityButton(city,temp){
    var btn = document.createElement("button");
    btn.innerHTML = city; 
    btn.style.float = "left";
    btn.style.height = "100px";
    btn.style.width = "100px";
    btn.style.border = "solid grey 1px";
    btn.style.fontSize = "1,5em";
    btn.setAttribute("onclick","setTemperature('"+temp+"');");
      
    cityDiv.appendChild(btn);
}


function setTemperature(temperature){
    console.log(temperature);
    if (temperature > -20 && temperature < 40){
        var valueDiv = document.getElementById("temperature-value");
        valueDiv.innerHTML = temperature + "°C";
        
        var fillDiv = document.getElementById("thermometer-fill");
        fillDiv.style.height = 5*temperature+110+"px";

        var colorDiv = document.getElementsByClassName("mercury");
        for (var i = 0; i < colorDiv.length; i++){
            if (temperature <= 0)
            colorDiv[i].style.backgroundColor='blue';
        else
            colorDiv[i].style.backgroundColor='red';
        }
    }
}


var cityDiv = document.getElementById("cities");
for( var city in cityTemperatures){
    console.log("city",city,"temp", cityTemperatures[city]);
    addCityButton(city,cityTemperatures[city]);
};