Home/ Questions/Q 8905559
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-06-15T02:25:33+00:00

All, I’m working with this Ajax tutorial which basically pull some records from a

  • 0

All,

I’m working with this Ajax tutorial which basically pull some records from a database and display them. I want to modify the code with a button that will show the records one by one instead of together. The behavior I want to achieve is to get the next record each time the user clicks the Show next button.

To do that I have built a little counter in the Ajax function that is used as an index to decide which array element to print. This doesn’t work. **My question is: why doesn’t my counter work?

Here is the html and Ajax code:

<html>
<body>
<script type="text/javascript">
<!-- 
function createRequest() {
  //Returns HttpRequest
    return request;
  }

//My attempt at a counter.  This doesn't work.
var index=null;

function calcIndex(){
  if(index==null){
    index=0;
  }else{
    index += index;
  }
  return index;
}
(.....)

</body>
</html>
Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    Your calcIndex function declaration is broken, it’s missing the function part. And are you sure you want to set index += index? That would be sort of odd. Not only that, even if you fix it and leave it as-is, index will never increment past zero:

    var index=null;

function calcIndex(){
  if(index==null){
    index=0;            // First call, now index = 0
  }else{
    index += index;     // Second, third, ... nth call: index = 0 + 0
  }
  return index;
}

    Let’s simplify:

    var index = 0;
function calcIndex(){
    return index++;   // Returns zero first, then 1, then 2...
}

    But wait, at that point why do you need a function at all? Instead you can simply do:

    var index = 0;
...
//index = calcIndex();  No point here
var queryString = "?age=" + age + "&wpm=" + wpm + "&sex=" + sex + "&index=" + index++;
                                                                              ^^^^^^^^

    Cheers

    • 0