How to Set Default Selected Value in Dropdown Using JavaScript

One of the common requirement is setting a default selected value in a dropdown menu.

In this article, we will discuss the different techniques and methods to complete this using JavaScript.

If you are a beginner or an professional developer, this article will help you to understand how to set a default selected value in a dropdown using JavaScript.

Understanding Dropdowns

The dropdown menus, also known as select elements, offer users with a list of options to select from.

These elements are widely used in web forms, allowing users to make selections based on their preferences.

By default, dropdowns do not have a preselected value. However, there are cases where you might want to set a default value to guide users or prepopulate the dropdown with a consistent option.

Selecting the Default Value

Before we move on into JavaScript methods, it is important understand how default values work in dropdowns.

The default value is defined by the selected attribute within the HTML option tags.

When the selected attribute is started, that choice will be preselected when the dropdown is provided on the page.

Method 1: Using JavaScript to Set Default Value

To automatically set a default value in a dropdown using JavaScript, you can utilize the power of the Document Object Model (DOM).

The DOM enables us to manipulate HTML elements and their attributes dynamically.

By targeting the dropdown element and modifying the selected attribute of the desired option, we can achieve the desired default value.

Here’s an example code:

// Select the dropdown element
const dropdownExample = document.getElementById('SampleDropdown');

// Set the desired option as the default value
dropdownExample.value = 'defaultOptionExample';

In this example code, we first recover the dropdown element using its unique identifier (id).

Then, we assign the proper option’s value to the value property of the dropdown.

This simple JavaScript code will make sure that the described option is selected by default when the dropdown is carried out.

Method 2: Handling Dynamic Dropdowns

In some scenarios, dropdowns may be constantly populated based on user interactions or data fetched from an external source.

When handling with dynamic dropdowns, it’s essential to set the default value after the options have been loaded.

// Select the dropdown element
const dropdownExample = document.getElementById('SampleDropdown');

// Populate the dropdown dynamically
fetch('https://example.com/options')
  .then(response => response.json())
  .then(options => {
    // Add options to the dropdown

    // Set the desired option as the default value
    dropdownExample.value = 'defaultOption';
  });

In this example code, we first fetch the choice asynchronously from an API endpoint.

Once the choice are available, we add them to the dropdown constantly. After the options have been added, we set the proper option as the default value using JavaScript.

Method 3: Using a Loop to Set Default Value

If you have a massive number of choices in a dropdown, setting the default value using individual statements for each choice can be time-consuming and error-prone.

In such cases, using a loop can shorten the process and make the code more maintainable.

Here’s an example code:

// Select the dropdown element
const dropdownExample = document.getElementById('SampleDropdown');

// Set the desired option as the default value
for (let option of dropdownExample.options) {
  if (option.value === 'defaultOption') {
    option.selected = true;
    break;
  }
}

In the above code example, we iterate through each choice of the dropdown using a for…of loop.

Then, we check if the choices value matches the proper default option and set the selected attribute to true.

Once the proper choice is found and selected, we break out of the loop to prevent unessential iterations.

FAQs

Conclusion

In conclusion, setting a default selected value in a dropdown using JavaScript is a simple requirement in web development.

By utilizing the power of the DOM, you can easily manipulate the selected attribute of the proper option to obtain the proper default selection.

In this article, we have also discussed the different methods, including direct assignment, dynamic population, and using loops, to set default selected values in dropdowns.

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