Salesforce Lightning Interview Questions I

1. What are the different types of Lightning events?

• Browser: browser notifications that are triggered by user interaction with an element. Eg. onClick
• System: fired by LC framework during LC lifecycle. They notify component states. Eg. init, render, afterRender
• Navigation: force:navigateToURL, force:createRecord, force:editRecord
• Component: A component event is fired from an instance of a component. A component event can be handled by the component that fired the event or by a component in the containment hierarchy that receives the event.
• Application: Application events follow a traditional publish-subscribe model. An application event is fired from an instance of a component. All components that provide a handler for the event are notified.

2. How to register, fire and handle a component and application event?

<aura:registerEvent name="componentEventFired" type="c:compEvent"/>
<aura:registerEvent name="appEvent" type="c:appEvent"/>

var compEvents = cmp.getEvent("componentEventFired");
compEvents.setParams({ "context" : parentName });
compEvents.fire();

var appEvent = $A.get("e.c:appEvent");
appEvent.setParams({ "context" : parentName });
appEvent.fire();
...
...
...
...
...
<aura:handler event="c:appEvent" action="{!c.handleApplicationEventFired}"/>
<aura:handler name="componentEventFired" event="c:compEvent" 
 action="{!c.handleComponentEventFired}"/>

{
 handleComponentEventFired : function(cmp, event) {
  var context = event.getParam("context");
 },

 handleApplicationEventFired : function(cmp, event) {
  var context = event.getParam("context");
 }
}

For more details, check the link below:
http://hellosnl.blogspot.in/2017/06/lightning-advanced-events-example.html


3. Let's say that you have an app myApp.app that contains a component myCmp.cmp with a ui:button component. During initialization, the init() event is fired in what order?
Answer: ui:button, ui:myCmp, and myApp.app.


4. Why do we use @AuraEnabled annotation?

• Use @AuraEnabled on Apex class static methods to make them accessible as remote controller actions in your Lightning components.
• Use @AuraEnabled on Apex instance methods and properties to make them serializable when an instance of the class is returned as data from a server-side action

5. Why do we use $A.enqueueAction(action)?
It adds the server-side controller action to the queue of actions to be executed. Rather than sending a separate request for each individual action, the framework processes the event chain and batches the actions in the queue into one request. The actions are asynchronous and have callbacks.


6. What is Namespace?
It is used to group related components together.


7. What is LockerService?
It enhances security by isolating Lightning components in their own namespace. A component can only traverse the DOM and access elements created by a component in the same namespace.


8. Examples of how to use some of the out-of-the-box events to enable component interation within your Lightning components?

$A.get("e.force:refreshView").fire(): reloads all data for the view.

createRecord : function (component, event, helper) {
    var createRecordEvent = $A.get("e.force:createRecord");
    createRecordEvent.setParams({
        "entityApiName": "Contact"
    });
    createRecordEvent.fire();
}

editRecord : function(component, event, helper) {
    var editRecordEvent = $A.get("e.force:editRecord");
    editRecordEvent.setParams({
         "recordId": component.get("v.contact.Id")
   });
    editRecordEvent.fire();
}

9. What is Lightning CLI?
It is a Heroku Toolbelt plugin that lets you scan your code for general JavaScript coding issues and lightning-specific issues.


10. Difference between bound and unbound expressions.
Bound expression {!expression}

• Any change to the value of the childAttr attribute in c:child also affects the parentAttr attribute in c:parent and vice versa.
• When you use a bound expression, a change in the attribute in the parent or child component triggers the change handler in both components.

Unbound expression {#expression}

• Any change to the value of the childAttr attribute in c:child doesn’t affect the parentAttr attribute in c:parent and vice versa.
• When you use an unbound expression, the change is not propagated between components so the change handler is only triggered in the component that contains the changed attribute.

For more details, check this link: http://hellosnl.blogspot.in/2017/05/data-binding-between-components.html


11. Use of THIS CSS class?
This adds namespacing to CSS and helps prevent one component's CSS from blowing away another component's styling.


12. How to set the value of an inherited attribute?
Use the <aura:set> tag.


13. What are the different ways to conditionally display markup, and what is the preferred approach?
Using the <aura:if> tag
Use CSS to toggle visibility of markup by calling $A.util.toggleClass(cmp, 'class') in JavaScript code.


14. What is $Resource global value provider? Is it possible to obtain a reference to a static resource in Javascript code?
It lets you reference images, style sheets, and JavaScript code you’ve uploaded in static resources.
To obtain a reference to a static resource in JavaScript code, use $A.get('$Resource.resourceName').
For more details, check this link http://hellosnl.blogspot.in/2017/04/lightning-using-static-resources.html


15. Let’s say you have several buttons that reuse the same onclick handler. How will you retrieve the name of the button that fired the event?
http://hellosnl.blogspot.in/2017/05/which-button-was-pressed.html


16. What are the names of interfaces that are added to a Lightning component to allow it to be used as custom tabs, and to be used in Lightning and Community builder?
http://hellosnl.blogspot.in/2017/05/configuring-lightning-components.html


17. What is the use of force:hasRecordId interface?
Add the force:hasRecordId interface to a Lightning component to enable the component to be assigned the ID of the current record.
The recordId attribute is set only when you place or invoke the component in a context of a record. For example, when you place the component on a record page, or invoke it as an action from a record page or object home. In all other cases, such as when you create this component programmatically inside another component, recordId isn’t set, and your component shouldn’t depend on it.


18. How to delete a design attribute for a component that implements the flexipage:availableForAllPageTypes or forceCommunity:availableForAllPageTypes interface?
First remove the interface from the component before deleting the design attribute. Then reimplement the interface. If the component is referenced in a Lightning page, you must remove the component from the page before you can change it.


19. How to add Lightning components to your Visualforce pages?
https://developer.salesforce.com/docs/atlas.en-us.lightning.meta/lightning/components_visualforce.htm

Javascript Accessor Properties

There are two different types of properties: data properties and accessor properties.

• Data properties contain a value.
• Accessor properties don’t contain a value but instead define a getter function and a setter function.

const person1 = {
   _name: "Nicholas",

   get name() {
      console.log("Reading name");
      return this._name;
   },

   set name(value) {
      console.log("Setting name to %s", value);
      this._name = value;
   }
};

console.log(person1.name);   // "Reading name" then "Nicholas"

person1.name = "Greg";
console.log(person1.name);   // "Setting name to Greg" then "Greg"

This example defines an accessor property called name. There is a data property called _name that contains the actual value for the property.

The leading underscore is a common convention to indicate that the property is considered to be private, though in reality it is still public. The syntax used to define the getter and setter for name looks a lot like a function but without the function keyword. The special keywords get and set are used before the accessor property name, followed by parentheses and a function body.

Javascript Object properties

Detecting Properties

The in operator looks for a property with a given name in a specific object and returns true if it finds it.

console.log("name" in person1);   // true
console.log("age" in person1);    // true
console.log("title" in person1);  // false

Keep in mind that methods are just properties that reference functions, so you can check for the existence of a method in the same way.

const person1 = {
   name: "Nicholas",
   sayName: function() {
      console.log(this.name);
   }
};

console.log("sayName" in person1);  // true

In some cases, however, you might want to check for the existence of a property only if it is an own property. The in operator checks for both own properties and prototype properties, so you’ll need to take a different approach. Enter the hasOwnProperty() method, which is present on all objects and returns true only if the given property exists and is an own property.

const person1 = {
   name: "Nicholas",
   sayName: function() {
      console.log(this.name);
   }
};

console.log("name" in person1);                         // true
console.log(person1.hasOwnProperty("name"));            // true

console.log("toString" in person1);                     // true
console.log(person1.hasOwnProperty("toString"));        // false

Removing Properties

You need to use the delete operator to completely remove a property from an object.

const person1 = {
   name: "Nicholas"
};

console.log("name" in person1);  // true

delete person1.name;             // true - not output
console.log("name" in person1);  // false
console.log(person1.name);       // undefined

Enumeration

By default, all properties that you add to an object are enumerable, which means that you can iterate over them using a for-in loop. This example uses bracket notation to retrieve the value of the object property and output it to the console, which is one of the primary use cases for bracket notation in JavaScript.

var property;

for (property in object) {
   console.log("Name: " + property);
   console.log("Value: " + object[property]);
}

If you just need a list of an object’s properties, use Object.keys() method to retrieve an array of enumerable property names. Typically, you would use Object.keys() in situations where you want to operate on an array of property names and for-in when you don’t need an array.

var properties = Object.keys(object);

// if you want to mimic for-in behavior
var i, len;

for (i=0, len=properties.length; i < len; i++){
   console.log("Name: " + properties[i]);
   console.log("Value: " + object[properties[i]]);
}

Keep in mind that not all properties are enumerable. You can check whether a property is enumerable by using the propertyIsEnumerable() method, which is present on every object:

var person1 = {
   name: "Nicholas"
};

console.log("name" in person1);    // true
console.log(person1.propertyIsEnumerable("name"));  // true

var properties = Object.keys(person1);

console.log("length" in properties);    // true
console.log(properties.propertyIsEnumerable("length")); // false

How to access map value in lightning component

Scenario: I have to create a picklist in Lightning, the values of which will be fetched from an already defined custom setting. The Apex method will be returning a map of values.

Define a method in Apex class SampleController which will return a map of values.

@AuraEnabled
public static Map<String, String> getselectOptions() {
    Map<String, CustomSettingName__c> values = CustomSettingName__c.getAll();
    Map<String, String> options = new Map<String, String>();
    
    for (String key: values.keyset()) {
        options.put(key, values.get(key).CustomSetting_Column__c);
    }
    return options;
}

Now in client side controller, create a new array optionsList. Add the values to this new array from the response object returned.

var optionsList = [];
for (var key in response) {
    if (response.hasOwnProperty(key)) {
        optionsList.push({value: key, label: response[key]});
    }
};
component.set('v.optionsList', optionsList);

Once the array is populated with the values, using aura:iteration tag populate the picklist values as below:

<aura:component controller="SampleController">
    
    <aura:attribute name="optionsList" type="List"/>

    <lightning:select name="selectItem" label="text" onchange="{!c.checkOptionValue}" value="{!v.partnerTypeSelected}" >
        <aura:iteration items="{!v.optionsList}" var="option">
            <option value="{!option.value}" text="{!option.label}" 
                    selected="{!option.selected}">
            </option>
        </aura:iteration>
    </lightning:select>
    
</aura:component>

Salesforce Security: Concepts

Salesforce Security Layers

1. Organization: Login IP ranges, Login hours; when where how can a user login to the org
2. Object: Object-level security; what action can a user have on a specific object
3. Field: Field-level security; what field can a user read/edit
4. Record: Sharing; what records can a user access

From an architect’s perspective, data access in Salesforce falls into 2 main categories:

• Object-level access, which includes field-level access
• Record-level access

Profiles and Permission Sets determine the object level security access to each object in Salesforce.

Read object-level security doesn't give Read access to all account records, it only gives the ability to read account records.

Profiles

A profile contains the baseline permissions of a user, and each user is assigned only 1 profile. It defines a user’s ability to peform different functions, access records, and the way the records are displayed. Profiles are tied to a user license.

Enhanced profile user interface lets you search for any setting and it can take you to this setting page. This can be set up in Setup —> User Management Settings.

Permission Set

A permission set is a collection of permissions that can be assigned to a user extending users’ functional access without changing their profiles. Users can have only one profile but they can have multiple permission sets.

Permission Set Group (PSG): It is a collection of permission sets. Users with a PSG receive the combined permissions of all the permission sets in the group. You can also remove individual permissions from a group with the muting feature, to further customize the group. Please note that a PSG can only contain 1 muting permission set that is created within the group.

A profile doesn’t provide the appropriate mechanism for scalable permission assignment. Permission sets and PSG are used to avoid the creation of many different profiles that are only slightly different.

List of permissions that are missing in a permission set

• Page layout assignment
• Login hours and Login IP ranges
• Desktop client access
• Session settings
• Password policies
• Delegated Authentication
• 2-factor authentication with SSO
• Organization-wide email addresses are assignable by profiles only
• Default record type per object
• Profile specific search layouts

Record Ownership

Every record must be owned by a single user or queue. The owner has access to the record, based on the object settings of the owner’s profile. Queue members and users higher in a role hierarchy can access queues from list views and take ownership of records in a queue.

Record ownership and full access are synonymous and interchangeable and provide the user with the highest level of access to a record.

Sharing (record-level access)

Record-level access determines which records a user can see for a specific object. Object-level security should allow to access this record.

• Organization-Wide Defaults
• Role Hierarchy
• Sharing Rules
• Manual Sharing
• Team Sharing
• Territory Hierarchy Access

For each object, the View All and Modify All permissions ignore sharing rules and settings.

View All Data and Modify All Data administrative permissions apply to all objects’ records.

Organization-wide Defaults (OWD)

OWD sharing settings specify the default level of access users have to each others’ records. OWD are the only way to restrict record access. You use OWD settings to lock down your data to the most restrictive level, and then use other sharing tools to selectively give access to other users. For each object, the OWD can be:

• Private
• Public read only
• Public read/write
• Public read/write/transfer: available for cases and leads
• Public full access: available for campaigns
• Controlled by parent

Role Hierarchy

Users can access the data of all the users directly below them in the hierarchy (subordinates) using the Grant Access Using Hierachies option. Managers gain as much access as their subordinates. This access applies to records owned by users, as well as records shared with them.

Public Group

A public group is a collection of individual users, roles, territories, and so on, that all have a function in common.

Groups can be nested (group A nested into group B), but keep in mind that nesting has an impact on group maintenance and performance due to group membership calculation. Don’t nest more than 5 levels. As a best practice, keep the total number of public groups for an organization to 100,000.

Sharing Rules

They allow for exceptions to OWD settings and the role hierarchy that give additional users access to records they don’t own. There are 2 types of sharing rules:

1. Ownership-based: records are shared following criteria based on their owner. For example, share all opportunities owned by user A with Group B. As a best practice, keep the number of ownership-based rules per object to 1000.
2. Criteria-based: they provide access to records based on the record’s field values.

Manual Sharing

Gives user the flexibility to share specific records with users that need to see them. To grant access to a record, you must be one of the following users:

• The record owner
• A user in a role above in the hierarchy
• Any user granted Full Access to the record
• An administrator

Team Sharing

For accounts, opportunities and cases, record owners can use teams to allow other users access to their records. The record owner adds team members and specifies the level of access each team member has to the record, so that some team members can have read-only access and others can have read-write access. The record owner can also specify a role for each team member.

Using Dynamic Apex to retrieve Picklist Values

USECASE: Fetch the picklist values from Industry field of Account sObject.

List<SelectOption> options = new List<SelectOption>();

Schema.DescribeFieldResult fieldResult = Account.Industry.getDescribe();
List<Schema.PicklistEntry> picklistEntries = fieldResult.getPicklistValues();

for (Schema.PicklistEntry picklistEntry : picklistEntries) {
    options.add(new SelectOption(picklistEntry.getLabel(), picklistEntry.getValue()));
}

return options;

OR

List<SelectOption> options = new List<SelectOption>();

Map<String, Schema.SObjectField> fieldMap = Account.getSObjectType().getDescribe().fields.getMap();
List<Schema.PicklistEntry> picklistEntries = fieldMap.get('Industry').getDescribe().getPickListValues();

for (Schema.PicklistEntry picklistEntry : picklistEntries) {
    options.add(new SelectOption(picklistEntry.getLabel(), picklistEntry.getValue()));
}

return options;

DescribeSObjectResult: Check whether the object is Custom or Standard

List<String> allCustomObjsList = new List<string>();
List<String> allStandardObjsList = new List<string>();

for(Schema.SobjectType obj : Schema.getGlobalDescribe().values()) {
    Schema.DescribeSobjectResult objResult = obj.getDescribe();
    if(objResult.isCustom()) {
        String strObjName =objResult.getname();
        allCustomObjsList.add(strObjName);
    }
    else {
        String strObjName =objResult.getname();
        allStandardObjsList.add(strObjName);
    }
}

System.debug('Custom Objects List: ' +allCustomObjsList);
System.debug('Standard Objects List: ' +allStandardObjsList);

If you need to check for a specific object, execute the below code:

Schema.DescribeSObjectResult describeAccount = Schema.sObjectType.Account;
System.debug(describeAccount.isCustom());

Similarly you can use other methods for describing sObjects, the list of which can be found below:
https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_methods_system_sobject_describe.htm

Fetch recordType Name and recordTypeId without SOQL

To avoid SOQL Limit we can use dynamic apex to get RecordTypeId. We can get a particular RecordTypeId of a particular sObject or get all recordTypeid of one sobejct in a map.

global class RecordTypeUtils {
    
    //Method to get the recordTypeId 
    public static Id recordTypeId(string obj,string recName){
        Id recTypeId;
        if(obj!= null && recName != null){
            recTypeId= Schema.getGlobalDescribe().get(obj).getDescribe().getRecordTypeInfosByName().get(recName).getRecordTypeId();
        }  
        return recTypeId;  
    }
    
    //Method to get the map of recordType Name as key and recordTypeId as value 
    public static Map<String,Id> recordTypeMap(string obj){
        Map<String,Id> recTypeNameWithIdMap=new Map<String,Id>();
        if(obj!= null){
            for(Schema.RecordTypeInfo recInfo : Schema.getGlobalDescribe().get(obj).getDescribe().getRecordTypeInfosByName().values()){
                recTypeNameWithIdMap.put(recInfo.getName(),recInfo.getRecordTypeId());
            }
        }
        return recTypeNameWithIdMap;
    } 
}

I created a record type "NewLabel" on Account object. Enter the below Apex code in Execute Anonymous window and check the output:

Map<String,Id> recTypeIdMap=RecordTypeUtils.recordTypeMap('Account');
System.debug(recTypeIdMap);
Id recId=RecordTypeUtils.recordTypeId('Account','NewLabel');
System.debug(recId);

Id recordTypeId = Schema.SObjectType.Account.getRecordTypeInfosByName().get('NewLabel').getRecordTypeId(); 
System.debug(recordTypeId);

Note that values of recId and recordTypeId in your output is same.

Check the link below to check a utility class that performs the query against the RecordType object
https://interactiveties.com/blog/2016/recordtype-utility-class.php

Apex: Get sObject details using ID

Id id = 'a0M7F000000qXgg';
Schema.sObjectType objType = id.getSObjectType();
Schema.DescribeSObjectResult objDescribe = objType.getDescribe();

System.debug(objDescribe.getName());

Similarly, you can get other sObject details using the methods described in the link below:
https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_methods_system_sobject_describe.htm

Dynamic SOQL and SOSL

To create a dynamic SOQL query at run time, use the database query method. Check the reference link for more details.

List<sObject> sobjList = Database.query(string);

To create a dynamic SOSL query at run time, use the search query method. For example:

String searchquery = 'FIND \'Edge*\' IN ALL FIELDS RETURNING Account(Id, Name), Contact, Lead';
List<List<SObject>>searchList = search.query(searchquery);

To prevent SOSL injection, use the escapeSingleQuotes method. This method adds the escape character (\) to all single quotation marks in a string that is passed in from a user. The method ensures that all single quotation marks are treated as enclosing strings, instead of database commands.

fieldList = (fieldList!=null) ? String.escapeSingleQuotes(fieldList) : fieldList;

References:
http://metillium.com/2016/03/variable-binding-in-dynamic-soql/

Salesforce Custom Settings

Custom settings are similar to custom objects and enable application developers to create custom sets of data, as well as create and associate custom data for an organization, profile, or specific user. Custom Settings data is stored in the application cache, which enables efficient access without the cost of multiple repeated queries to the database. As long as you query the Custom Settings using GET methods rather than an SOQL query you can retrieve all of the values with literally zero impact on the governor’s count of the number of queries performed or rows retrieved.

List Custom Settings

It provides a reusable set of static data that can be accessed across your organization. Data in list settings does not vary with profile or user, but is available organization-wide.

The following are instance methods for list custom settings.

• getAll(): Returns a map of the data sets defined for the custom setting.
• getInstance(dataSetName) / getValues(dataSetName): Returns the custom setting data set record for the specified data set name.

Hierarchy Custom Settings

It uses a built-in hierarchical logic that lets you "personalize" settings for specific profiles or users. The hierarchy logic checks the organization, profile, and user settings for the current user and returns the most specific value. In the hierarchy, settings for an organization are overridden by profile settings, which, in turn, are overridden by user settings.

References:
http://www.brcline.com/blog/salesforce-custom-settings
https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_methods_system_custom_settings.htm

Lightning Component for attaching files using input file component

A rough markup of this component using input type file component. Please refer the previous article to get an idea of how the helper JS and the apex class is formed.

<div class="slds-form-element">
    <span class="slds-form-element__label" id="file-selector-id">Attachment</span>
    <div class="slds-form-element__control">
        <div class="slds-file-selector slds-file-selector_files">
            <div class="slds-file-selector__dropzone">
                <input type="file" class="slds-file-selector__input slds-assistive-text" accept="image/png" id="file-upload-input-01" aria-describedby="file-selector-id" aura:id="file" onchange="{!c.showfile}"/>
                <label class="slds-file-selector__body" for="file-upload-input-01">
                    <span class="slds-file-selector__button slds-button slds-button_neutral">
                        <c:svgIcon class="slds-button__icon slds-button__icon_left" xlinkHref="/resource/slds232/assets/icons/utility-sprite/svg/symbols.svg#upload" />
                        Upload Files
                    </span>
                    <span class="slds-file-selector__text slds-medium-show">or Drop Files</span>
                </label>
            </div>
        </div>
    </div>
</div>

showfile:function(component,event,helper){
    helper.show(component,event);
    
    var f = event.target.files[0]; 
    var fileInput = component.find("file").getElement();
    var file = fileInput.files[0];
    
    var reader = new FileReader();
    reader.onloadend = function(e) {
        var contents = e.target.result;
        var base64Mark = 'base64,';
        var dataStart = contents.indexOf(base64Mark) + base64Mark.length;
        var fileContents = contents.substring(dataStart);
        
        helper.upload(component, file, encodeURIComponent(fileContents), function(answer) {
            if (answer) {
                helper.hide(component,event);
            }
            else{
            }
        });
    }
    reader.readAsDataURL(file);
}

Lightning Component for attaching files using lightning:input

<aura:component description="FileUploader" controller="FileUploadController">
    <aura:attribute name="fileToBeUploaded" type="Object[]"/>
    <lightning:spinner aura:id="mySpinner" class="slds-hide"/>
    
    <div class=" slds-box">
        <div class="slds-grid slds-wrap">
            <lightning:input aura:id="file-input" type="file"
                             files="{!v.fileToBeUploaded}"
                             onchange="{!c.onFileUploaded}"
                             accept="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
                             label="Attachment"
                             name="file" multiple="true"/>
        </div>
    </div>
</aura:component>

({
    onFileUploaded:function(component,event,helper){
        helper.show(component,event);
        var files = component.get("v.fileToBeUploaded");
        if (files && files.length > 0) {
            var file = files[0][0];
            var reader = new FileReader();
            reader.onloadend = function() {
                var dataURL = reader.result;
                var content = dataURL.match(/,(.*)$/)[1];
                helper.upload(component, file, content, function(answer) {
                    if (answer) {
                        helper.hide(component,event);
                        // Success
                    }
                    else{
                        // Failure
                    }
                });
            }
            reader.readAsDataURL(file);
        }
        else{
            helper.hide(component,event);
        }
    }
})

({
    upload: function(component, file, base64Data, callback) {
        var action = component.get("c.uploadFile");
        console.log('type: ' + file.type);
        action.setParams({
            fileName: file.name,
            base64Data: base64Data,
            contentType: file.type
        });
        action.setCallback(this, function(a) {
            var state = a.getState();
            if (state === "SUCCESS") {
                callback(a.getReturnValue());
            }
        });
        $A.enqueueAction(action);
    },
    show: function (cmp, event) {
        var spinner = cmp.find("mySpinner");
        $A.util.removeClass(spinner, "slds-hide");
        $A.util.addClass(spinner, "slds-show");
    },
    hide:function (cmp, event) {
        var spinner = cmp.find("mySpinner");
        $A.util.removeClass(spinner, "slds-show");
        $A.util.addClass(spinner, "slds-hide");
    }
})

public class FileUploadController {
    @AuraEnabled
    public static Id uploadFile(String fileName, String base64Data, String contentType) { 
        base64Data = EncodingUtil.urlDecode(base64Data, 'UTF-8');
        Attachment a = new Attachment();
        a.parentId = '0017F000007xoiVQAQ';
        a.Body = EncodingUtil.base64Decode(base64Data);
        a.Name = fileName;
        a.ContentType = contentType; 
        insert a;
        System.debug(a.Id);
        return a.Id;
    }
}

NOTE: For demo purpose, I have hardcoded the value of an account '0017F000007xoiVQAQ' in the apex class. In actual scenario, you should get this ID from the component.