JS在页面限制checkbox最大复选数

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应该是挺简单的代码, 记录一下分享.

首先最直接的想法就是使用循环, 用局部变量记录已选的checkbox, 达到最大值就将余下的checkbox都禁止选择, 如下:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" ""><html xmlns=""><head><meta http-equiv="Content-Type" content="text/html; charset=gb2312" /><title>JS限制checkbox复选框多选</title><script language="javascript" type="text/javascript">function onCheckBox(checkbox){var items = document.getElementsByName("item");var maxChoices = 3;var flag = 0;for(var i=0; i<items.length; i++){if(items[i].checked){flag ++;}}if(flag >= maxChoices){for(var k=0; k<items.length; k++){if(!items[k].checked){items[k].disabled = true;}}}else{for(var p=0; p<items.length; p++){if(!items[p].checked){items[p].disabled = false;}}}}function onSubmitVote(){var items = document.getElementsByName("item");var choices = 0;var maxChoices = 3;for(var j=0; j<items.length; j++){if(items[j].checked){choices ++;}}if(choices == 0){alert("请选择选项再提交");}else if(choices > maxChoices){alert("选择选项不能超过 "+ maxChoices + "个");}else{alert("提交成功");}}</script></head><body >JS限制checkbox复选框多选<br><br><input type="checkbox" value="value1" name="item" onClick="onCheckBox(this);"/> 选项一 <br><input type="checkbox" value="value2" name="item" onClick="onCheckBox(this);"/> 选项二 <br><input type="checkbox" value="value3" name="item" onClick="onCheckBox(this);"/> 选项三 <br><input type="checkbox" value="value4" name="item" onClick="onCheckBox(this);"/> 选项四 <br> <input type="checkbox" value="value5" name="item" onClick="onCheckBox(this);"/> 选项五 <br><br><input type="button" id="submit_vote" name="submit_vote" value="提交" onClick="onSubmitVote()" /></body></html>

运行如下:

效果是没问题, 但通常第一想法都是比较粗糙的, 好的东西需要加以雕琢. 上面用的的是局部变量, 所以每次进入js的onCheckBox()都是新的变量, 还要循环几次, 但换成全局变量, 每次进入, flag的值都是继续上次操作的值, 那么可以减少循环的次数了. 针对该部分做修改, 如下:

<script language="javascript" type="text/javascript">var maxChoices = 3;var flag = 0;function onCheckBox(checkbox){var items = document.getElementsByName("item");//var maxChoices = 3;//var flag = 0;if(checkbox.checked){flag ++;}else{flag --;}if(flag < maxChoices){for(var i=0; i<items.length; i++){if(!items[i].checked){items[i].disabled = false;}}}else{for(var i=0; i<items.length; i++){if(!items[i].checked){items[i].disabled = true;}}}}function onSubmitVote(){var items = document.getElementsByName("item");var choices = 0;//var maxChoices = 3;for(var j=0; j<items.length; j++){if(items[j].checked){choices ++;}}if(choices == 0){alert("请选择选项再提交");}else if(choices > maxChoices){alert("选择选项不能超过 "+ maxChoices + "个");}else{alert("提交成功");}}</script>

这样效果是一样的, 但循环就少一次.

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