How to determine whether a check box is selected in javascript_javascript skills

Previously I summarized the issue about how jquery determines whether a check box is selected . Today I summarized how to determine whether a js check box is selected
JavaScript determines whether the checkbox is selected. The following is an example (there is now a set of checkboxes as follows):

<input type="checkbox" name="fruit" value="apple" />苹果 
<input type="checkbox" name="fruit" value="orange" />橘子 
<input type="checkbox" name="fruit" value="banana" />香蕉 
<input type="checkbox" name="fruit" value="grape" />葡萄 

The method to get the value of a set of checkboxes with name=fruit is as follows:

<script language="javascript"> 
function checkbox(){ 
  var str=document.getElementsByName('fruit'); 
  var strstrLen=str.length; 
  var checkVal=''; 
  for (i=0;i<strLen;i++){ 
    if(str[i].checked==true){ 
      checkVal+=str[i].value+','; 
    } 
  } 
  if(checkVal==''){ 
    alert("请先选择复选框～！"); 
  }else{ 
    alert("复选框的值是："+checkVal); 
  } 
} 
</script> 

Combine it with the previous "JQuery method to determine whether a check box is selected" and learn together, you will definitely have unexpected gains!