Javascript和复选框

Question

I'm trying to create a checkbox which will alter the form action on click. I'm starting out by setting it to alert a message depending on whether it is checked or not but nothing is happening. Please help me!

JavaScript:

function toggleAction(){
var check = document.getElementById('checkb').checked;
   if (checked == "1"){
    alert("is checked");
   }else{
    alert("is not checked"); }
}

HTML:

<INPUT TYPE="checkbox" id="checkb" onclick="toggleAction()">Add Another<br>

Answer 1

Your main problem is that you named your variable check but then in your if statement looked for checked . Secondarily, note that .checked is a boolean value ( true or false ) but you are comparing it to the string "1". This happens to work, but is not recommended.

Try:

if (check) alert("is checked");
else       alert("is not checked");

Better than using getElementById explicitly in your handler, also, is to use the reference to the checkbox handling the event:

document.getElementById('checkb').onclick = toggleAction;
function toggleAction(){
  if (this.checked) alert('yes');
  else              alert('no');
}

Note in the above how I also assigned the event handler programmatically using JavaScript instead of using the onclick="..." HTML attribute. This is considered a "best practice"; you should not be writing JavaScript directly in your HTML.

Answer 2

if(checked == "1")应为if(check) 。