javascript - How to reset jQuery variable based on selected element? -

i created html rubric allows user select cell , have add earned points versus points possible. right now, have function allows 1 td per row selected. when cell selected, adds points variable. issue is, when change selection row, adds new selection on top of variable, doesn't subtract , replace value.

for example, if had 8 point selection made, change 6, instead of variable value being 6, adds 6 8.

the function have add points follows:

jquery('#ldrm-rubric-loaded td.choice').click(function () {     // obtain points earned     var ndx = jquery(this).index() + 1;     var target = jquery('#ldrm-rubric-loaded thead tr.points th:nth-child('+ndx+')').html();     if(!isnan(target) && target.length != 0) {         pointsearned += parsefloat(target);     }     jquery('#ldrm-points-earned').html('points earned: '+pointsearned);     alert(pointsearned); }); 

http://jsfiddle.net/f6u2pjgu/1/

any ideas on how alter function replace value instead of adding on it?

i think easier if use single handler like

var total = 0,     $headers = jquery('#ldrm-rubric-loaded thead tr.points th'); jquery('#ldrm-rubric-loaded td.choice').click(function () {     var $this = jquery(this),         $prev;     if (!$this.hasclass('selected')) {         $prev = $(this).siblings('.selected').removeclass('selected');          if ($prev.length) {             total -= +$headers.eq($prev.index()).html() || 0;         }         total += +$headers.eq($this.index()).html() || 0;          $this.addclass('selected');         jquery(this).siblings().removeclass('selected');         var trackchanges = jquery('#ldrm-rubric-loaded').clone().html();         jquery('#ldrm_assignment_content').val(trackchanges);           jquery('#ldrm-points-earned').html('points earned: ' + total);         alert(total);     } //else don't since selected  }); 

demo: fiddle

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if want retain code structure

jquery('#ldrm-rubric-loaded td.choice').click(function () {     var $this = jquery(this),         $tr = $this.closest('tr'),         prevvalue = $tr.data('selected') || 0;      // obtain points earned     var ndx = $this.index() + 1;     var value = +jquery('#ldrm-rubric-loaded thead tr.points th:nth-child(' + ndx + ')').html() || 0;     pointsearned -= prevvalue;     pointsearned += value;      $tr.data('selected', value)     jquery('#ldrm-points-earned').html('points earned: ' + pointsearned);     alert(pointsearned); }); 

demo: fiddle