Dropdown inside textbox/textarea

I am looking for something similar to friends filter in facebook. When you type '@' inside text area it shows you a list of friends to select. I have tried to search for dropdown inside textbox, but was not able to find what I was looking for.

How do I activate a TextBox if I select an option in drop down box?

When an item (option) is selected in DropDownList (HTML SELECT), the EnableDisableTextBox JavaScript function is executed. Inside this function, based on whether the Other option (item) is selected, the TextBox will be enabled else disabled. The HTML Markup consists of a DropDownList (HTML SELECT) and a TextBox.

How do I create a dropdown form in HTML?

The <select> element is used to create a drop-down list. The <select> element is most often used in a form, to collect user input. The name attribute is needed to reference the form data after the form is submitted (if you omit the name attribute, no data from the drop-down list will be submitted).