The selectedIndex property of the HTMLOptionsCollection interface is the numeric index of the first selected <option> element, if any, or −1 if no <option> is selected. Setting this property selects the option at that index and deselects all other options in this collection, while setting it to -1 deselects any currently selected elements. It is exactly equivalent to the selectedIndex property of the HTMLSelectElement that owns this collection.
A number.
const optionColl = document.getElementById("select").options;
console.log(`selected option: ${optionColl.selectedIndex}`); // the index of the first selected option, or -1 if no option is selected
optionColl.selectedIndex = 0; // selects the first item
optionColl.selectedIndex = -1; // deselects any selected option
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Opera | Safari | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | WebView Android | WebView on iOS | |
selectedIndex |
1 | 12 | 1 | ≤12.1 | 3 | 18 | 4 | ≤12.1 | 1 | 1.0 | 4.4 | 1 |
HTMLOptionsCollection.lengthHTMLOptionsCollection.add()HTMLOptionsCollection.remove()HTMLOptionsCollectionHTMLOptionElementHTMLOptGroupElementHTMLSelectElement
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https://developer.mozilla.org/en-US/docs/Web/API/HTMLOptionsCollection/selectedIndex