如何在JavaScript中修复Uncaught TypeError？

Question

I'm trying to submit a form of a specific element in my webpage but i get a

Uncaught TypeError: Cannot read property 'form' of undefined

This is the JavaScript script for my webpage

<script type="text/javascript">
              var aTags = document.getElementsByName("s");
    for (var i=0;i<aTags.length;i++){
        aTags[i].addEventListener('click', function(e){
          e.preventDefault();
          bootbox.confirm({
    message: "This is a confirm with custom button text and color! Do you like it?",
    closeButton: false,
    buttons: {
        confirm: {
            label: 'Yes',
            className: 'btn-success'
        },
        cancel: {
            label: 'No',
            className: 'btn-danger'
        }
    },
    callback: function (result) {
      if(result){
        aTags[i].form.submit();
      }
    }
});
        });
            }
              </script>

Answer 1

Every one of the click handlers is referencing the exact same i variable. By the time the button is clicked, i has long ago been incremented to aTags.length . So aTags[i] resolves to aTags[aTags.length] , which is undefined.

Simplest solution is to just use let instead of var . That way, every time through the loop gets a new binding of the variable, and thus the click handlers are all associated with the correct value.

for (let i = 0; i < aTags.length; i++){
   // rest of the code the same
}