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); }); }); });

user400654 · Accepted Answer · 2012-05-23 14:11:54Z

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.

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.

Rory McCrossan · Accepted Answer · 2012-05-23 14:11:32Z

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']; });

j_freyre · Accepted Answer · 2012-05-23 14:10:12Z

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...

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