js obtains the selected Option by default and is not the currently selected value_javascript skills

<script> <br>function getDefaultSelectedOption(selectId, valIfNull) { <br>var dom, selectId = selectId.replace(/^#/, ''), opts; <br>try { <br>opts = document.getElementById(selectId).getElementsByTagName('option'); <br>for (var i in opts) { <br>if (opts[i].defaultSelected) { <br>dom = opts[i]; <br>break; <br>} <br>} <br>} catch (e) { <br>} <br>return dom||valIfNull; <br>} <br></script>

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test
<script> <br>function getDefaultSelectedOption(selectId, valIfNull) { <br>var dom, selectId = selectId.replace(/^#/, ''), opts; <br>try { <br>opts = document.getElementById(selectId).getElementsByTagName('option'); <br>for (var i in opts) { <br>if (opts[i].defaultSelected) { <br>dom = opts[i]; <br>break; <br>} <br>} <br>} catch (e) { <br>} <br>return dom||valIfNull; <br>} <br></script>
<script> <br>document.getElementById('btn').onclick = function () { <br>alert((getDefaultSelectedOption('sel1', {})).value); <br>}; <br></script>