Drop down list 和 Comb box 的区别

参考：http://stackoverflow.com/questions/2176297/is-there-any-difference-between-drop-down-box-and-combo-box

原文：

A combo box is a commonly-used graphical user interface widget. It is a combination of a drop-down list or list box and a single-line textbox, allowing the user to either type a value directly into the control or choose from the list of existing options.

While the definition of drop-down list matches exactly what the HTML <SELECT> element does:

When activated, it displays (drops down) a list of values, from which the user may select one.

• a combo box is a combination of an input text field and a list of options. You can type in stuff in the input field and the list should update to highlight a possible match
• a dropdown is just a list of options that drops down when you click on the arrow button. You can only choose from a list of predefined options

就是说：

combo box 是一个 文本输入框 和 一个 列表或下拉列表 的 组合。用户可以在文本输入框中输入内容（这时combo box可以有以下行为：combo box的列表可以在它的所有选项中寻找匹配项，并高亮显示一个可能的匹配项）

下拉列表（drop down list）是一个选项的列表，当用户点击drop down list时，会展开一个一个“下拉”的列表，用户可以从列表中选择一项。这些选项都是预先定义好的，用户只能从中选择，不能自己输入新的内容。