Chained State city dropdown list from JSON - json

Question

I am trying to populate a chained State City select dropdowns. I am using an external json file to do so, which consists of State and their corresponding city name, id and pincode. Can somebody gimme some idea on how to achieve this. I need to populate the city and pincode value based on the state selection. Thanks in advance...
JSON
{
"Alaska" : [
{"id": "1", "name": "Adak", "pincode": "xxx1"},
{"id": "2", "name": "Akhiok", "pincode": "xxx2" },
{"id": "3", "name": "Akiak", "pincode": "xxx3" },
],
"Arizona" : [
{"id": "4", "name": "Apache Junction", "pincode": "xxx4"},
{"id": "5", "name": "Avondale", "pincode": "xxx5"},
{"id": "6", "name": "Benson", "pincode": "xxx6"},
],
"Alabama" : [
{"id" : "5", "name": "Abbeville", "pincode": "xxx7" },
{"id" : "7", "name": "Adamsville", "pincode": "xxx8" },
{"id" : "8", "name": "Akron", "pincode": "xxx9" },
]
}
Final rendered html
<select id="state">
<option value="1">Alaska</option>
<option value="2">Arizona</option>
<option value="3">Alabama</option>
</select>
<select id="city">
<option value="4">Adak</option>
<option value="5">Akhiok</option>
<option value="6">Akiak</option>
</select>
<input id="pincode" type="text" />

Answer 1

I find your question interesting and wrote the corresponding solution which you can see live here.
Here is the code:
jQuery(document).ready(function () {
var myData;
var onCityChange = function (e) {
var cityData = $("option:selected", e.target).data('pincode');
$("#pincode").val(cityData.pincode);
};
var onStateChange = function (e) {
var state = $("option:selected", e.target).text();
if (state && myData) {
var stateData = myData[state];
if (stateData && stateData.length > 0) {
$("#city").empty();
$("#city").unbind('change');
for (var i = 0; i < stateData.length; i++) {
var cityData = stateData[i];
var option = $('<option value="' + cityData.id + '">' + cityData.name + '</option>')
.data('pincode', cityData);
$("#city").append(option);
}
$("#city").bind('change', onCityChange)
.trigger('change');
}
}
};
$.ajax({
url: 'DependendSelectsFromJson.json',
dataType: 'json',
success: function (data) {
var stateOptions = "", stateId = 1;
for (var prop in data) {
if (data.hasOwnProperty(prop)) {
stateOptions += '<option value="' + stateId + '">' + prop + '</option>';
stateId++;
}
}
myData = data;
$("#state").html(stateOptions)
.bind('change', onStateChange)
.trigger('change');
}
});
});
to get access about the pincode of the second (city) select box I used jQuery.data function which I find very practical if one need to associate some additional information with an DOM element. One could save only pincode value in the way, but I used the function to save full information about the city.
UPDATED: I forgot to mention that the JSON data which you posted has errors. You should remove commas before ']'. Probably it is just a problem with cut&paste of the data to the text of the question.

Answer 2

there are many ways.
global Varible option.
var json_object = {
"Alaska" : {}
}; //and the rest of other text too lazy to type :)
$('#state').change(function(){
var state = $(this).val();
cities = json_object[state];
$('#city').html('');//remove the prev elements
for(item in cities){//same as foreach in php
$('<option value=""></option>').appendTo($('#city'));
}
});
i must admit is not complete but giving you the rough idea.
Other wise use ajax like so
$('#state').change(function(){
var url = 'ajax.php';//should return json with a list of cities only
var state = $('#state').val();
var data = {'state':state};
$.ajax({
url:url,
data:data,
dataType:'json',
success: function(items){
//do something with it
}
})
});
The only thing you need to know is that both have their advantages and disadvantages.
first option : can only fire one request but loads sh*t loads of data that are not needed.
second option: makes more request but less data