In this blog post we will understand how we can develop a custom select box dependent dropdown using javascript on us details
About Select Box Dependent Dropdown
In this blog post we will learn how to create a custom dropdown menu using JavaScript based on US location details like Country State and City.
Mastering any program begins with creating a Select Box Dependent Dropdown using logic and gaining a perfect understanding of it before converting it into code. Start by creating a JSON file called list.json.
JSON File (list.json)
This JSON file is used to store some static data in an array that contains states and names as keys. Names Key then contains an array of multiple cities representing that state in the US. By default the country will be the US
Fetch API to get list content in JSON array
To obtain the content from the list.json file we will make use of the fetch API request to retrieve all the data from the file. The fetch API is a built in JavaScript API that is commonly used to retrieve any kind of result.
Adding Functionality To Select Boxes
When handling select boxes in JavaScript we use an event listener to collect the value from selected options. We add an "on change" event listener to get their values.
Getting Select Box Values Using onchange Listener
First We Get the Default value of the country select box so whenever someone clicks on country. A list of states appears in the second states select box. Know we use ForEach Loop in JavaScript to iterate each value and display them in the states select box while validating any duplicate value inside an array.
Then again we add on change event listener to states dropdown and this time we will use our logic to check the specific clicked value inside the names array to display corresponding values of cities inside the city dropdown or select box. For This we will loop two times using forEach. The first loop will give us the keys through these keys we then loop the names array. If the value matches we will display the cities inside the city dropdown. For finding the selected value we use includes() function in javascript which helps us to search for a specific selected value.
In the city case we also check for duplicate values so in this case our complete dependent dropdown in javascript will be ready. Read the steps to follow to get a complete overview in a short
Steps to Follow
1. Writing the HTML code
2. Creating a beautiful layout using CSS
3. Integrating JavaScript into the code
4. Adding an onchange event listener to select boxes
5. Fetching content from the list.json file
5. Fetching content from the list.json file
7. Validating for duplicate values
8. Using "includes" to match the values
9. That's it!
Final Conclusion
Through Reading This Complete Blog Post You will understand the logic behind dependent dropdowns and be able to create any kind of dependent dropdown using JavaScript. For More Clarification Watch the Complete YouTube video that clears all concepts that you read inside this blog post.
