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HTMLSelectElement.selectedIndex - Web APIs 编辑

The HTMLSelectElement.selectedIndex is a long that reflects the index of the first or last selected <option> element, depending on the value of multiple. The value -1 indicates that no element is selected.

Syntax

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

Example

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')

// When a new <option> is selected
selectElem.addEventListener('change', function() {
  var index = selectElem.selectedIndex;
  // Add that data to the <p>
  pElem.innerHTML = 'selectedIndex: ' + index;
})

Specifications

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