Multiple Dependent Drop Down List in JavaScript

This code provides the functionality to create multiple dependent drop-down lists in JavaScript. The drop-down lists are populated dynamically based on the user’s selection.

Whether you need to gather information related to categories, subcategories, product attributes, or any other interconnected data, this code offers a powerful and user-friendly solution. It helps you to create a cascading or dependent drop-down list where the options in one drop-down depend on the selection made in another drop-down.

How to Create Multiple Dependent Drop Down Lists using JavaScript

1. Create the HTML structure for multiple dependent drop-down lists as follows:

<div class="container">
        <h2>Multi Level Dependent Drop Down</h2>

        <form action="#">
            <select name="" id="country">
                <option value="">-- Select Country --</option>
            </select>
            <select name="" id="state">
                <option value="">-- Select State --</option>
            </select>
            <select name="" id="city">
                <option value="">-- Select City --</option>
            </select>
            <select name="" id="zip">
                <option value="">-- Select Zip --</option>
            </select>
        </form>

    </div>

2. After that, define the basic CSS styles for the form and select dropdown. If you want to customize the select dropdown, check out this code project.

*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body{
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color: #EEEEEE;
}
.container{
    text-align: center;
}

.container h2{
    font-size: 2vw;
    font-family: 'Courier New', Courier, monospace;
    margin-bottom: 40px;
    letter-spacing: 1.2px;
}

form{
    display: flex;
    justify-content: center;
    align-items: center;
    flex-direction: column;
    gap: 15px;
}

form select{
    width: 450px;
    padding: 15px;
    padding-left: 10px;
    background-color: #fff;
    border-radius: 10px;
    border: none;
    outline: none;
    font-size: 1.2rem;
    box-shadow: 0 5px 10px 0 rgb(0,0,0,0.25);
    cursor: pointer;
}

3. Finally, add the following JavaScript code to your project and update options according to your needs.

var countrySateCityinfo = {
    Australia: {
        "Western Australia": {
            Broome: ["6725", "6318", "6701"],
            Coolgardie: ["6429", "6432"]
        },
        Tasmania: {
            Hobart: ["7000", "7520"],
            Launceston: ["7250", "7334"],
            Burnie: ["7320", "7315"]
        }
    },
    Germany: {
        Bavaria: {
            Munich: ["80331", "80333", "80335"],
            Numemberg: ["90402", "90403", "90404"]
        },
        Hessen: {
            Frankfurt: ["60306", "60309", "60310"],
            Surat: ["55246", "55247", "55248", "55249"]
        }
    },

    Canada: {
        Alberta: {
            Calgary: ["8033", "8333", "8035"],
            Edmonton: ["9040", "9403", "9040"]
        },
        Manitoba: {
            Brandon: ["6030", "6030"],
            Winnipeg: ["5524", "5547", "5248"]
        }
    }
    
}

window.onload = function(){
    const selectCountry = document.getElementById('country'),
        selectState = document.getElementById('state'),
        selectCity = document.getElementById('city'),
        selectZip = document.getElementById('zip'),
        selects = document.querySelectorAll('select')

        selectState.disabled = true
        selectCity.disabled = true
        selectZip.disabled = true

        selects.forEach(select => {
            if(select.disabled == true){
                select.style.cursor = "auto"
            }
            else{
                select.style.cursor = "pointer"
            }
        })

        for(let country in countrySateCityinfo){
            // console.log(country);
            selectCountry.options[selectCountry.options.length] = new Option(country, country)
        }


        // country change
        selectCountry.onchange = (e) =>{
            
            selectState.disabled = false
            selectCity.disabled = true
            selectZip.disabled = true

            selects.forEach(select => {
                if(select.disabled == true){
                    select.style.cursor = "auto"
                }
                else{
                    select.style.cursor = "pointer"
                }
            })

            selectState.length = 1
            selectCity.length = 1
            selectZip.length = 1

            for(let state in countrySateCityinfo[e.target.value]){
                // console.log(state);
                selectState.options[selectState.options.length] = new Option(state, state)
            }
        }

        // state change
        selectState.onchange = (e) =>{
            selectCity.disabled = false
            selectZip.disabled = true

            selects.forEach(select => {
                if(select.disabled == true){
                    select.style.cursor = "auto"
                }
                else{
                    select.style.cursor = "pointer"
                }
            })

            selectCity.length = 1
            selectZip.length = 1

            for(let city in countrySateCityinfo[selectCountry.value][e.target.value]){
                // console.log(city);
                selectCity.options[selectCity.options.length] = new Option(city, city)
            }
        }

        // change city
        selectCity.onchange = (e) =>{
            selectZip.disabled = false

            selects.forEach(select => {
                if(select.disabled == true){
                    select.style.cursor = "auto"
                }
                else{
                    select.style.cursor = "pointer"
                }
            })
            
            selectZip.length = 1

            let zips = countrySateCityinfo[selectCountry.value][selectState.value][e.target.value]
            
            for(let i=0; i<zips.length; i++){
                selectZip.options[selectZip.options.length] = new Option(zips[i], zips[i])
            }
        }
}

That’s all! hopefully, you have successfully created multiple dependent drop down list using JavaScript. If you have any questions or suggestions, feel free to comment below.