How do I get this loop to work? It's returning undefined angualrjs

Question

I am trying to extract the ID from an object which is at 0 in the index in the object. I need to then convert this key to a string to be able to pass it into an api endpoint.

My Controller event:

        $scope.attach = function () {                 
        var rules_id = $scope.rules.selected;
        if (rules_id) {
            var l = rules_id.length;
            for (var i = 0, j = l; i < j;)
            {
              var key_value = rules_id[i]; 
            }              
        }
        console.log($scope.rules);
        console.log(key_value);
        console.log($scope.rules.selected);
        console.log($scope.asset.id);

    };

At present, I am just trying to define each variable in the console, the only thing returning undefined is the loop variable "key_value".

I have checked this against a number of examples and standard setups for a loop and this isn't working.

$scope.rules.selected is a checkbox result which key is represented by a rule ID. See below:

<form name="rules" method="post">
   <table class="table table-striped table-hover" ng-model="associated_rules">
    <thead>
      <th>Rule ID:</th>
       <th>Rule Types:</th>
         <th>Description:</th>
           <th>Start Time:</th>
              <th>End Time:</th>
                 <th>Apply Rule to Vehicle:</th>
    </thead>
    <tr ng-repeat="associated_rule in associated_rules">
         <td>@{{ associated_rule.id }}</td>
         <td>@{{ associated_rule.resource_ids.accounts }}</td>
         <td>@{{ associated_rule.description }}</td>
         <td>@{{ associated_rule.start_time }}</td>
         <td>@{{ associated_rule.end_time }}</td>
         <td><input type="checkbox" ng-model="rules.selected[associated_rule.id]"aria-label="associated_rule.id" ng-true-value="true"ng-false-value="false" value="rules.selected"></td></tr>
  </table>
 <button class="btn btn-primary" ng-click="attach()"><i class="fa fa-paperclip"></i> Attach</button>
 </form>

Answer 1

On this approach we take some well-formed input and do some transformations so we can do a better use of it

    // creates the module
    angular.module("samplemodule",[])

    // apppend the controller to the module
    angular.module("samplemodule").controller("SampleCtl",function(){

      // log data from somewhere
      this.originalData = [
        "{db77370c-fbfe-11e5-8468-ed8c21fd14a1: true, c9f2c76c-fbfe-11e5-8fe5-70c120bc96b5: true}",
        "{db77370c-fbfe-11e5-8468-ed8c21fd14a2: false, c9f2c76c-fbfe-11e5-8fe5-70c120bc96b6: true}",
        "{db77370c-fbfe-11e5-8468-ed8c21fd14a3: true, c9f2c76c-fbfe-11e5-8fe5-70c120bc96b7: true}",
        "{db77370c-fbfe-11e5-8468-ed8c21fd14a4: true, c9f2c76c-fbfe-11e5-8fe5-70c120bc96b8: false}",
        
      ]
      
      this.values = this.originalData.map(function(e){
        e = e.replace(/{/g,"{\"").replace(/:/g,"\":").replace(/, /g,", \"")
        e = JSON.parse(e)
        var kv = []
        for(var attr in e)
          kv.push({key:attr,value:e[attr]})
        return kv
      })
      
      this.attach = function attach(){
        var selectedones = [].concat.apply([],this.values).filter(function(e){
          return e.value
        })
        alert(selectedones)
      }
    })

    <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>
    <div ng-app="samplemodule" ng-controller="SampleCtl as ctl">
      <table>
        <tbody>
          <tr ng-repeat="vl in ctl.values">
            <td ng-repeat="kv in vl">
              {{kv.key}}
              <input type="checkbox" ng-model="kv.value"/>
            </td>
          </tr>
        </tbody>
      </table>
      <button ng-click="ctl.attach()">The selected ones</button>
    </div>

Answer 2

What you want maybe can archived if you rethink in a more declarative way:

// creates the module
angular.module("samplemodule",[])

// apppend the controller to the module
angular.module("samplemodule").controller("SampleCtl",function(){

  this.values = [// sample data
    {a:"XXX",b:0,c:new Date(),d:true },
    {a:"XXY",b:1,c:new Date(),d:false},
    {a:"XYX",b:2,c:new Date(),d:false},
    {a:"XYY",b:3,c:new Date(),d:true },
    {a:"YXX",b:4,c:new Date(),d:false},
    {a:"YXY",b:5,c:new Date(),d:false}
  ]
  
  this.attach = function attach(){
    var selectedones = this.values.filter(function(e){ 
      return e.d // just the selected ones
    }).map(function(e){
      return e.b // just the ids or anything you want
    }).join(",")
    alert(selectedones)
  }
})

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>
<div ng-app="samplemodule" ng-controller="SampleCtl as ctl">
  <table>
    <thead>
      <tr>
        <th>A</th>
        <th>B</th>
        <th>C</th>
        <th></th>
      </tr>
    </thead>
    <tbody>
      <tr ng-repeat="vl in ctl.values">
        <td>{{vl.a}}</td>
        <td>{{vl.b}}</td>
        <td>{{vl.c}}</td>
        <td><input type="checkbox" ng-model="vl.d"/></td>
      </tr>
    </tbody>
  </table>
  <button ng-click="ctl.attach()">The selected ones</button>
</div>

Answer 3

Your for loop is wrong, also you are trying to console log a variable that is declared inside the for loop, it will always be undefined! This is the correct for loop example:

for (i = 0; i < rules_id.length; i++) {
    console.log(rules_id[i]); 
}

Please have a read on how for loop works

But the real problem here is with your Angular Code