javascript - 在更改之前获取select（下拉列表）的值(Getting value of select (dropdown) before change)

Question

The thing I want to achieve is whenever the <select> dropdown is changed I want the value of the dropdown before change.

(我想要实现的是每当<select>下拉列表被更改时我想要更改之前的下拉列表的值。)

I am using 1.3.2 version of jQuery and using on change event but the value I am getting over there is after change.

(我正在使用1.3.2版本的jQuery并使用更改事件，但我在那里得到的值是在更改后。)

<select name="test">
<option value="stack">Stack</option>
<option value="overflow">Overflow</option>
<option value="my">My</option>
<option value="question">Question</option>
</select>

Lets say currently option My is selected now when I change it to stack in the onchange event (ie when I changed it to stack) I want it's previous value ie my expected in this case.

(让我们说当前我选择My当我在onchange事件中将其更改为堆栈时（即当我将其更改为堆栈时）我想要它的先前值，即我在这种情况下的预期。)

How can this be achieved?

(怎么能实现这一目标？)

Edit: In my case I am having multiple select boxes in the same page and want same thing to be applied to all of them.

(编辑：在我的情况下，我在同一页面中有多个选择框，并希望将相同的内容应用于所有这些框。)

Also all of my select are inserted after page load through ajax.

(此外，我的所有选择都是在通过ajax加载页面后插入的。)

  ask by Alpesh translate from so

Answer 1

Combine the focus event with the change event to achieve what you want:

(将焦点事件与更改事件相结合，以实现您的目标：)

(function () {
    var previous;

    $("select").on('focus', function () {
        // Store the current value on focus and on change
        previous = this.value;
    }).change(function() {
        // Do something with the previous value after the change
        alert(previous);

        // Make sure the previous value is updated
        previous = this.value;
    });
})();

Working example: http://jsfiddle.net/x5PKf/766

(工作示例： http ： //jsfiddle.net/x5PKf/766)