Looping through Json object

Question

I am trying to only print a unique value of 'sum' by doing a compare at the end of the loop, but I'm seeing that every time it does a compare it has already moved on to the next element and therefore when its comparing the two values they're always the same. Is there another way to do this?

 $(document).ready(function(){
 $.getJSON('XML.php', function(data) {
 JSON.stringify(data);
 var prevCardCode = '';
 $.each( data, function(index, element){
 var prevCardCode = element['CardCode'];
 if (!(element['CardCode'] == prevCardCode)) {
 var sum = element['payment_sum'] + '<br/>';
 $('#showdata').append(sum);
 }
 alert(element['CardCode'] + 'compare' + prevCardCode);
 });
 });
});

Answer 1

The var keyword doesn't belong within the each in this case, and you need to move it to after the comparison.

var prevCardCode = '';
$.each(data, function(index, element) {
 if (!(element['CardCode'] == prevCardCode)) {
 var sum = element['payment_sum'] + '<br/>';
 $('#showdata').append(sum);
 }
 alert(element['CardCode'] + 'compare' + prevCardCode);
 prevCardCode = element['CardCode'];
});​

If the var is left in place before prevCardCode, it will never set the one defined outside of the $.each and will not carry over to the next iteration of $.each.

• user400654: I thought I did explain it pretty well. Basically, if you include the var keyword, you are creating a new variable within the scope of the $.each rather than using the existing variable in the parent scope. Additionally, you need to compare the value before you override it for the next iteration.

Answer 2

You need to move the prevCharCode assignment to the end of the loop and remove the var in front of it:

var prevCardCode = '';
$.each( data, function(index, element) {
 if (!(element['CardCode'] == prevCardCode)) {
 // your code...
 }
 prevCardCode = element['CardCode'];
});

Answer 3

prevCardCode is not the precedent element but the current... Then you compare current with current...

If you want to compare precedent element with current, you should use a while or a do while.

var i = 1;
var precedentEl = array[0];
while (i < array.length) {
 // Do some stuff like compare current and precedent
 precedentEl = array[i];
 i++;
}

Secondly, you call XML.php which return json... It's sound strange...