<script language="javascript"><!--//checkbox元素的名字前綴，本例為sample1,sample2,sample3...var sctrlprefix = "sample";//checkbox元素?cái)?shù)量，本例有10個(gè)；var imaxcheckbox = 10;//設(shè)置最大允許選擇的數(shù)量；var imaxselected = 3;function docheck(ctrl) {var inumchecked = 0;var thisctrl;var i;//初始化i = 1;//循環(huán)直到選中了最多的checkbox;while ((i <= imaxcheckbox) && (inumchecked <= imaxselected)) {thisctrl = eval("ctrl.form." + sctrlprefix + i);if ((thisctrl != ctrl) && (thisctrl.checked)) {inumchecked++;}i++;}// 檢查是否達(dá)到了最大選擇數(shù)量；if (inumchecked == imaxselected) {// 如果是則uncheck剛選擇的元素；ctrl.checked = false;alertxt="最多可選"+imaxselected+"個(gè)"alert(alertxt);}}// --></script><form name="form" method="post"><input type="checkbox" name="sample1" onclick="docheck(this)">a<input type="checkbox" name="sample2" onclick="docheck(this)">b<input type="checkbox" name="sample3" onclick="docheck(this)">c<input type="checkbox" name="sample4" onclick="docheck(this)">d<input type="checkbox" name="sample5" onclick="docheck(this)">e<input type="checkbox" name="sample6" onclick="docheck(this)">f<input type="checkbox" name="sample7" onclick="docheck(this)">g<input type="checkbox" name="sample8" onclick="docheck(this)">h<input type="checkbox" name="sample9" onclick="docheck(this)">i<input type="checkbox" name="sample10" onclick="docheck(this)">j</form>
[ctrl+a 全部選擇 提示：你可先修改部分代碼，再按運(yùn)行]

<script language="javascript">var c=0,limit=3;function docheck(obj) {obj.checked?c++:c--;if(c>limit)obj.checked=false,c--;}</script><form name="form" method="post"><input type="checkbox" name="sample1" onclick="docheck(this)">a<input type="checkbox" name="sample2" onclick="docheck(this)">b<input type="checkbox" name="sample3" onclick="docheck(this)">c<input type="checkbox" name="sample4" onclick="docheck(this)">d<input type="checkbox" name="sample5" onclick="docheck(this)">e<input type="checkbox" name="sample6" onclick="docheck(this)">f<input type="checkbox" name="sample7" onclick="docheck(this)">g<input type="checkbox" name="sample8" onclick="docheck(this)">h<input type="checkbox" name="sample9" onclick="docheck(this)">i<input type="checkbox" name="sample10" onclick="docheck(this)">j</form>
[ctrl+a 全部選擇 提示：你可先修改部分代碼，再按運(yùn)行]

<script language="javascript">var c=0,limit=3;alertxt="最多可選"+limit+"個(gè)"function docheck(obj) {obj.checked?c++:c--;if(c>limit)obj.checked=false,c--,alert(alertxt);}</script><form name="form" method="post"><input type="checkbox" name="sample1" onclick="docheck(this)">a<input type="checkbox" name="sample2" onclick="docheck(this)">b<input type="checkbox" name="sample3" onclick="docheck(this)">c<input type="checkbox" name="sample4" onclick="docheck(this)">d<input type="checkbox" name="sample5" onclick="docheck(this)">e<input type="checkbox" name="sample6" onclick="docheck(this)">f<input type="checkbox" name="sample7" onclick="docheck(this)">g<input type="checkbox" name="sample8" onclick="docheck(this)">h<input type="checkbox" name="sample9" onclick="docheck(this)">i<input type="checkbox" name="sample10" onclick="docheck(this)">j</form>
[ctrl+a 全部選擇 提示：你可先修改部分代碼，再按運(yùn)行]