JS get the number of checkbox simple example _javascript skill

JS gets the number of marquee checkboxes selected.

var checkbox = Document.getelementsbyname ("likes[]"); 
This is the way to get multiple-selection boxes to be arrays.
                                            
//like is name = "like[]" and must be added []
var checked_counts = 0;

for (Var i=0;i<checkbox.length;i++) {
if (checkbox[i].checked) {     //Selected checkbox
checked_counts++
}

alert (checked_counts);

What I do is that every click on a multiple selection box to determine whether the current number of checked more than a certain number

function Checkdate () { 
  var n = $ ("#cart_q_num"). Val (); 
   var checkedcount=0; 
   var checkbox = Document.getelementsbyname ("tie_in[]");
   alert (checkbox.length);
   for (Var i=0;i<checkbox.length i + +) { 
   if (checkbox[i].checked) { 
     checkedcount++ 

     }} 
   } 
   alert (checkedcount);
    if (checkedcount>n) { 
       alert ("The quantity of the gifts should equal to the quantity of the sunglasses set."); 
      return false; 
   } else{
     $ ("#free_pro_selected_num"). HTML (checkedcount);
    }

To make the function checkdata () Work every click, you need to add the onclick event in the checkbox box:

The above JS to get the number of the checkbox is a simple example is a small series to share all the content, I hope to give you a reference, but also hope that we support the cloud-dwelling community.