html

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<select id="num">

<option value="0">请选择</option>

<option value="1">111</option>

<option value="2">222</option>

<option value="3">333</option>

<option value="4">444</option>

</select>

jQuery

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方法1：

var val = $('#num').val();

方法2：

var val = $('#num option:selected').val();