When I was working on a project today, I encountered a problem. I needed to display multiple checkboxes, but only up to 6 could be selected. After debugging for a long time, it finally came out. The code is as follows:
<SCRIPT LANGUAGE="JavaScript">
var c=0,limit=6;
function doCheck(obj) {
obj.checked?c++:c--;
if(c>limit){
obj.checked=false;
alert("over");
c--;
}
}
</SCRIPT>
<html>
<body>
<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
</body>
</html>The display results are as follows:
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
