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HTMLSelectElement.selectedIndex 是一个长整型数,它反映了被选中的第一个<option> 元素的索引值。值为-1时表明没有元素被选中。

 

语法

var index = selectElem.selectedIndex;
selectElem.selectedIndex = index;

实例

HTML

<p id="p">selectedIndex: 0</p>

<select id="select">
  <option selected>Option A</option>
  <option>Option B</option>
  <option>Option C</option>
  <option>Option D</option>
  <option>Option E</option>
</select>

JavaScript

var selectElem = document.getElementById('select')
var pElem = document.getElementById('p')

// 当有新的<option>元素被选中时
selectElem.addEventListener('change', function() {
  var index = selectElem.selectedIndex;
  // 把index数据添加到p元素中
  pElem.innerHTML = 'selectedIndex: ' + index;
})

Specifications

Specification Status Comment
HTML Living Standard
HTMLSelectElement
Living Standard No change since the latest snapshot, HTML5.
HTML5
HTMLSelectElement
Recommendation Initial definition, snapshot of HTML Living Standard.

浏览器兼容性

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