How to Dynamically Set the Selected Option in a select Element with JavaScript

Learn how to successfully change the selected option in a dynamically populated ` select ` element using JavaScript and jQuery.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Adding an option to select with Javascript

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Dynamically Set the Selected Option in a <select> Element with JavaScript

If you are working with HTML forms, you might encounter situations where you need the user to select an item from a dropdown list. These dropdowns, created using <select> elements, can be populated dynamically using JavaScript or jQuery. However, changing the selected option afterward could be a challenge. In this article, we will discuss a common issue and how to resolve it, ensuring your dropdown behaves as expected.

The Problem

Imagine you have multiple <select> elements on your web page. One of these is dynamically populated with values coming from a JavaScript object, as shown below:

[[See Video to Reveal this Text or Code Snippet]]

Let's say you have successfully added options, but when you try to change the selected option with this code:

[[See Video to Reveal this Text or Code Snippet]]

It doesn't work as expected. In particular, you encounter the issue when you try to select an option that was added dynamically via JavaScript. You have the correct ID for the option you want to select, but nothing happens.

Understanding the Solution

The Timing Issue

The primary reason this code fails could be due to timing. In JavaScript, if you attempt to change the selected option before the dropdown options have been completely populated, the commands will not have any effect. Here’s how to make sure your code runs in the right order:

Position your code strategically: Ensure the code that selects the option runs after the options have been populated. This might entail placing it right after the loop or in a callback if you are performing asynchronous operations.

Example Implementation

Below is a complete example that illustrates the correct way to implement this. Let's assume heritages is an object holding your data:

[[See Video to Reveal this Text or Code Snippet]]

Complete HTML Snippet

For a complete picture, here is how the HTML and Javascript would look in a single file:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By ensuring that the code to change the selected option runs only after the dropdown has been fully populated, you can successfully manipulate the <select> elements on your page using JavaScript and jQuery. Remember to address the timing of your script execution and you'll avoid this common pitfall. Happy coding!