Explanation of the principle of determining whether multiple elements (RADIO, CHECKBOX, etc.) are selected_Form special effects

When submitting a form, you often need to check whether some required fields are empty.
If it is a text box, it is easy to handle. Everyone can write it, but if you encounter multiple raids, checkbox
must select one or more This one is a little more troublesome.
By taking the set of elements of the entire form, we can process it as follows:

Copy code The code is as follows:

var msg="";
var obj="";
var flag=false;
for (var i=0;ivar e = document.frmsignup.elements[i];
if (e.name == 'source'){
if (e.checked==false)
flag= false;
else{
flag=true;
break;
}
}
}
if (!flag) {
msg = "Access source: required Fill in."
obj = "source";
}

This just determines whether multiple radios with name="source" are selected,
For checkbox if you want After judging how many to choose, you only need to add a count to collect the results
If there is a simpler way, I hope you can let me know.