<select id="select"><option value="123">456</option>
</select>

var a = $('#select').val();    // 结果为 123var b = $('#select option:selected').val();    // 结果为 123var d = $('#select option:selected').attr('value');    // 结果为 123var c = $('#select option:selected').text();    // 结果为 456

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remove option 后 for循环添加

$("#selectId option").remove();
$("#selectId").append("<option value=''></option>");$.each(data, function (key, value) {$("#selectId").append("<option value='" + data[key].Id + "'>" + data[key].Name + "</option>")
})