我无法使用javascript大写输入文本框

Question

I am making a program wherein all textboxes are converted into UPPERCASE through CSS. In my Javascript, I want to pass it to server with the same values as UPPERCASE, too. However, I encountered an error:

"Uncaught TypeError: Cannot read property 'toUpperCase' of undefined"

I already tried different solutions from different users of StackOverFlow such as Uncaught TypeError: Cannot read property 'toUpperCase' of undefined but still error.

Here's my code:

  // put all gathered data in an array variable so as to send to the server for saving          
  var param = new Array();
  param[0] = clientType;
  param[1] = catv_provider;
  param[2] = existing_subs;
  param[3] = gender;
  param[4] = lastname;
  param[5] = firstname;
  param[6] = midname;
  var param2 = [];

  for (var i = 0; i < param.length; i++) {
    param2[i] = param[i].toUpperCase();
  }

Answer 1

It's because you are getting value undefined .

You can modify your loop as

    for (var i = 0; i < param.length; i++) {
     if(typeof(param[i])!=="undefined") { //skipping undefined
        param2[i] = param[i].toUpperCase();
     }
   }

Answer 2

Try Following

   for (var i = 0; i < param.length; i++) {
        if(param[i] != null){    
        param[i].toUpperCase();
     }
    }