How to define a field value of an object in javascript

Question

I have an iteration over the values of a picklist in a lightning component. It dynamically generates checkboxes for every value of this picklist.

I want to be able to use the value of this picklist to filter an array

When I apply this I get the error:

Action failed: c:checkboxFilter$controller$Techniek [opleidingen is not defined]

In this case Techniek is the fieldvalue on the object. How do I define a value of a field on an object

Here is my code Component

<aura:attribute name="opleidingen" type="Opleiding__c[]"/>  
<aura:attribute name="fieldName" Description="API Name of Picklist Value" type="String" />
<aura:attribute name="objectName" Description="API Name of the Object" type="Opleiding__c[]" />

<aura:attribute name="checkboxValue" type="Boolean" default="true" />

<aura:attribute name="records" type="object[]" description="" access="private" /> 
<div style="width:100%" class="slds-align_absolute-left">
    {!v.objectName}
    <aura:iteration items="{!v.records}" var="item" indexVar="indx"> 
        <ui:inputCheckbox aura:id="checkbox" 
                          value="{!item.checkboxValue}" 
                          text="{!item.fieldName}" 
                          name="{!indx}" 
                          label="{!item.fieldName}" 
                          change="{!c.Techniek}"/>&nbsp;{#item.val}     
    </aura:iteration> 

Javascript

 component.set("v.alleOpleidingen");
  var checkboxValue = event.getSource().get('v.value');// This is different in the documentation(Gianni).
  if(checkboxValue == true){
      console.log('Evaluates to true');

      var result = opleidingen.filter(function(opl)  {
                                      return typeof opl.Categorie__c === "{!v.label}";
                                      });
    component.set("v.Evaluates to true",result);  
     }    
  else{
  console.log('false');

I tried with JSON.stringify(opl.Categorie__c) but this give the same error

c:checkboxFilter$controller$Techniek [action is not defined]

Answer 1

The change attribute needs to reference a controller function (that you write) not a data field.

If Techniek is a custom field, you will need to include the __c too so Techniek__c.

Lightning Components support two way binding i.e. what is in the data model is presented on the screen and changes made on the screen are automatically pushed into the data model. So value="{!item.Techniek__c}" may be part of your solution.

I suggest you Google for examples that are close to what you are aiming to do and also go through some of the relevant Trailheads.