Ajax Form. Update Second Select when choose an opt

Question

I'm to to Javascript and I'm looking to make a form. I found some code that I edited but it doesn't work. What I'm trying to make is a form with 2 select dropdowns. When the visitor chooses one service from the first dropdown, then the 2nd dropdown will be automatically updated with the names of the staff of each service. I have uploded the code to jsFiddle. The url is http://jsfiddle.net/mrtxR/ . I thought it would be really simple but couldn't find any tutorial and guide on this.

// The data that the service should return
// JSFiddle will echo it back for us on that URL
var doctors = {
    success: true,
    doctors: [
        {
            id: 71,
            name: "George"
        },
        {
            id: 72,
            name: "James"
        }
    ]
}

// This is what your JSON from PHP should look like
var jsonDoctors = JSON.stringify(doctors);
console.log(jsonDoctors);

// Bind change function to the select
jQuery(document).ready(function() {
    jQuery("#services").change(onServiceChange);
});

function onServiceChange()
{
    var serviceId = jQuery(this).val();    

     $.ajax({
        url: '/echo/json/',
        type: 'post',
        data: {
            serviceId: serviceId,
            json: jsonDoctors // jsFiddle echos this back to us
        },
        success: onServicesRecieveSuccess,
        error: onServicesRecieveError
    });
}

function onServicesRecieveSuccess(data)
{
    // Target select that we add the states to
    var jTargetSelect = jQuery("#doctors");

    // Clear old states
    jTargetSelect.children().remove();

    // Add new states
    jQuery(data.doctors).each(function(){        
        jTargetSelect.append('<option value="'+this.id+'">'+this.name+'</option>');
    });
}

function onServicesRecieveError(data)
{
    alert("Could not get services. Please try again.");
}

Answer 1

Your last comment is correct, you should add serviceId to each doctor. Your fake javascript can look like:

// The data that the service should return
// JSFiddle will echo it back for us on that URL
var doctors = {
    success: true,
    doctors: [
        {
            id: 71,
            serviceId : 1,
            name: "George"
        },
        {
            serviceId : 2,
            id: 72,
            name: "James"
        },
        {
            serviceId : 3,
            id: 73,
            name: "Ron"
        },
        { 
            serviceId : 1,
            id : 77,
            name : "Barak",

        }
    ]
}

function getJsonDoctors(serviceId) {
    var result = [];
    var l = doctors.doctors;
    for (var i = 0 ; i < l.length ; i++) {
        if (l[i].serviceId == serviceId) {
            result.push(l[i]);   
        }
    }
    return JSON.stringify({success : true,doctors : result});
}

// This is what your JSON from PHP should look like
var jsonDoctors = JSON.stringify(doctors);
console.log(jsonDoctors);

// Bind change function to the select
jQuery(document).ready(function() {
    jQuery("#services").change(onServiceChange);
});

function onServiceChange()
{
    var serviceId = jQuery(this).val();    

     $.ajax({
        url: '/echo/json/',
        type: 'post',
        data: {
            serviceId: serviceId,
            json: getJsonDoctors(serviceId) // jsFiddle echos this back to us
        },
        success: onServicesRecieveSuccess,
        error: onServicesRecieveError
    });
}

function onServicesRecieveSuccess(data)
{
    // Target select that we add the states to
    var jTargetSelect = jQuery("#doctors");

    // Clear old states
    jTargetSelect.children().remove();

    // Add new states
    jQuery(data.doctors).each(function(){        
        jTargetSelect.append('<option value="'+this.id+'">'+this.name+'</option>');
    });
}

function onServicesRecieveError(data)
{
    alert("Could not get services. Please try again.");
}