js 判断数组中存在select option的值，则选中option

js 判断数组中存在select option的值，则选中option

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<select multiple size="5" id="sel">
    <script>
        for (var i = 1; i < 10; i++) document.write(' <option value="'+i+'">'+i+'</option>');
    </script>
</select>
<script>
    var arr = [2, 3, 7, 9],sel=document.getElementById('sel');
    for(var i=0;i<sel.options.length;i++)
        for (var j = 0; j < arr.length; j++) {
            if (sel.options[i].value == arr[j]) { sel.options[i].selected = true; break;}
        }
</script>