How can I set a default option for the select dropdown button in Webflow e-commerce using basic JavaScript lines?

To set a default option for the select dropdown button in Webflow e-commerce using basic JavaScript, you can follow these steps:

1. Identify the class or ID of the select dropdown button in your Webflow e-commerce site. You can find this by inspecting the element in your browser's developer tools. For example, let's say the class of the select dropdown button is "my-dropdown-button".

2. Create a JavaScript function that sets the default option for the select dropdown. This function will be called when the page loads. Here's an example of the JavaScript code you can use:

```javascript
function setDefaultOption() {
var dropdown = document.querySelector('.my-dropdown-button');
var defaultOption = dropdown.options[0]; // Change the index to correspond to the option you want as default

defaultOption.selected = true;
}
```

In this code, we first select the dropdown element using `document.querySelector('.my-dropdown-button')`, where `.my-dropdown-button` is the class name of the select dropdown button. You can replace it with the appropriate class or ID name.

Next, we select the option we want to set as the default. In this example, `dropdown.options[0]` selects the first option in the dropdown. You can change the index to correspond to the option you want as default, keeping in mind that JavaScript uses a zero-based index.

Finally, we set the `selected` property of the default option to `true`, which makes it the default selection when the page loads.

3. Call the `setDefaultOption()` function when the page loads. You can achieve this by adding an event listener for the `DOMContentLoaded` event. Here's an example:

```javascript
document.addEventListener('DOMContentLoaded', setDefaultOption);
```

This code ensures that the `setDefaultOption()` function is called once the page has finished loading.

By following these steps and customizing the class or ID names and the default option index to fit your specific use case, you can set a default option for the select dropdown button in Webflow e-commerce using basic JavaScript.