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Show city list as per state select in dropdown select box Javascript

<!DOCTYPE html>
<html>
<head>
<title></title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<script type="text/javascript">
var citiesByState = {
Odisha: ["Bhubaneswar","Puri","Cuttack"],
Maharashtra: ["Mumbai","Pune","Nagpur"],
Kerala: ["kochi","Kanpur"]
}
function makeSubmenu(value) {
if(value.length==0) document.getElementById("citySelect").innerHTML = "<option></option>";
else {
var citiesOptions = "";
for(cityId in citiesByState[value]) {
citiesOptions+="<option>"+citiesByState[value][cityId]+"</option>";
}
document.getElementById("citySelect").innerHTML = citiesOptions;
}
}
function displaySelected() { var country = document.getElementById("countrySelect").value;
var city = document.getElementById("citySelect").value;
alert(country+"\n"+city);
}
function resetSelection() {
document.getElementById("countrySelect").selectedIndex = 0;
document.getElementById("citySelect").selectedIndex = 0;
}
</script>
</head>
<body onload="resetSelection()">
<select id="countrySelect" size="1" onchange="makeSubmenu(this.value)">
<option value="" disabled selected>Choose State</option>
<option>Odisha</option>
<option>Maharashtra</option>
<option>Kerala</option>
</select>
<select id="citySelect" size="1" >
<option value="" disabled selected>Choose City</option>
<option></option>
</select>
<button onclick="displaySelected()">show selected</button>
</body>
</html>

Run it yourself

Demo