如何用js判断动态数组值是否为空
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javascript如何判断对象是否存在，具体代码如下：
查看代码?打印
1if(typeOf(x)=='undefined'){2????alert('undefined');3}else?if(typeOf(x)=='null'){4????alert('null');5}或者简单那的用法是
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查看代码?打印1if(!variable){}?
<tr?bgcolor="#FFFFFF">
<td?width="18%"?align="left"?nowrap><div?align="center">
??????????????<select?name="jy1">
?????????????? <option?value=""?selected></option>
????????????????<option?value="同意">同意</option>
????????????????<option?value="不同意">不同意</option>
??????????????</select>
??????????????<select?name="jy2">
????????????????<option?value=""?selected></option>
????????????????<option?value="通过">通过</option>
????????????????<option?value="不通过">不通过</option>
??????????????</select>
??</td>
</tr>
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应该是提交表单之前获取到这些数据
JavaScript code123456789101112131415161718192021222324function?check(){?var?jys1?=?document.getElementsByName("jy1");?var?jys2?=?document.getElementsByName("jy2");?var?a1?=?new?Array();var?a2?=?new?Array();for(var?i=0;i?<jys1.length;i++){?????for(var?j=0;j<jys1[i].length;j++)?????{???????if(jys1[i][i].selected)???????{?????????a1.push(jys1[i][i].value);???????}?????}}?for(var?i=0;i?<jys2.length;i++){?????for(var?j=0;j<jys2[i].length;j++)?????{???????if(jys2[i][i].selected)???????{?????????a2.push(jys2[i][i].value);???????}?????}}?}