获取选择框的选定值
我有选择框，并且选择的框选择了一个值，现在我可以更改值，我希望它应该选择更改的值而不是已经选择的值
我像这样使用它
var x= document.getElementById("numbervalue");
var y= document.getElementById("dayvalue");
ax = dnum.options[x.selectedIndex].value;
at = dDay.options[y.selectedIndex].value;上面只给我以前选择的值，而不是新的值
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呼啦一阵风
希望这有帮助<!DOCTYPE HTML><html><head><meta charset="utf-8"><title>get value of select box</title><style>body { font-family: Courier, monospace; }#output { margin-top:10px; text-align:center; padding:10px; width: 200px; height:100px; border-style:groove;}.info { font-size: 12px; width: 270px;}</style></head><body><h3>select box stack overflow</h3><p class = "info">On any change in an option element, the JS will use the vals from the numbervalue option element to reset the val in the dayvalue option element.<br><br>You must change the number to change anything</p><label for = "dayvalue">Choose a day:</label><select name="dayvalue" id="dayVal" onchange="readBoxes()"> <option value="m">Monday</option> <option value="t">Tuesday</option> <option value="w">Wednesday</option> <option value="th">Thursday</option> <option value="f">Friday</option> <option value="sat">Saturday</option> <option value="sun">Sunday</option></select><br><label for = "numbervalue">Choose a number:</label><select name="numbervalue" id="numVal" onchange="readBoxes()"> <option value="1">1</option> <option value="2">2</option> <option value="3">3</option> <option value="4">4</option> <option value="5">5</option> <option value="6">6</option> <option value="7">7</option></select> <div id="output">Day of Week</div><p>-h34dsp1nns</p><script>function readBoxes() { var out = document.getElementById("output"); var day = document.getElementById("dayVal"); var num = document.getElementById("numVal"); var numIndex = num.selectedIndex; day.selectedIndex = numIndex; //resets the index var dayVal = day[numIndex]; //gets the option element at an index out.innerHTML = dayVal.text;}</script></body></html>
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JavaScript