Converting Aura Components to Lightning Web Components (LWC)

The evolution of Salesforce development has introduced Lightning Web Components (LWC) as a modern framework built on web standards. While Aura components have been instrumental in building rich interfaces, transitioning to LWC offers improved performance, better developer experience, and alignment with modern web development practices. This article provides a detailed guide on Converting Aura Components to Lightning Web Components, tailored for Salesforce professionals seeking to modernize their applications.

Converting Aura Components to Lightning Web Components

Salesforce is growing and with it, Lightning Web Components (LWC) have become the latest framework to build responsive UI. Aura Components has been battle tested but moving to LWC will provide better performance, closer web standards alignment and a more consistent developer experience. Converting Aura Components to LWCs will help organizations utilize the latest developments making their applications future-ready.

Understanding the Differences Between Aura and LWC

Before diving into the conversion process, it’s crucial to understand the fundamental differences between Aura and LWC.

Aura Components

Aura components are part of the Aura framework, which is a component-based UI framework for developing dynamic web apps for mobile and desktop devices.

• Proprietary Framework: Uses Salesforce-specific components and syntax.
• Two-Way Data Binding: Supports two-way data binding between components and controllers.
• Event-Driven Architecture: Utilizes application and component events for communication.

Lightning Web Components

LWC is a modern framework built on native web standards. It leverages custom elements, templates, shadow DOM, and other new language constructs available in ECMAScript 7 and beyond.

• Standards-Based: Built on web standards without heavy abstraction.
• Performance: Faster rendering and better performance due to lightweight framework.
• One-Way Data Binding: Follows a unidirectional data flow.
• Shadow DOM: Encapsulates component styles and markup.

Steps to Convert Aura Components to LWC

The conversion process involves several steps, including analyzing the existing Aura component, mapping its functionality to LWC equivalents, and rewriting the code accordingly.

Step 1: Analyze the Aura Component

Begin by understanding the structure and functionality of the Aura component:

• Markup (.cmp file): Contains the component’s HTML structure and Aura markup.
• Controller (.js file): Handles client-side logic.
• Helper (.js file): Contains reusable functions.
• Style (.css file): Defines component-specific styles.
• Renderer (optional): Custom rendering logic.

Identify the features used in the component, such as attributes, methods, events, and Apex controllers.

Step 2: Map Aura Features to LWC Equivalents

Next, determine how Aura features translate to LWC:

Aura	LWC
aura:component	LightningElement class
Attributes (attribute)	Properties and @api decorator
Expressions in markup	Template expressions using curly braces
Event handling with Component.getEvent()	Custom events using standard DOM events
Calling server-side Apex	Wire adapters and imperative Apex calls
Two-way data binding	One-way data binding with event handlers

Step 3: Create the LWC Component Structure

Set up the basic files for the LWC component:

• componentName.html: Markup file.
• componentName.js: JavaScript file.
• componentName.js-meta.xml: Configuration file.
• componentName.css: (Optional) Stylesheet file.

Example LWC Component Structure

myComponent/
├── myComponent.html
├── myComponent.js
├── myComponent.js-meta.xml
└── myComponent.css (optional)

Step 4: Convert the Markup

Translate the Aura component’s markup to LWC template syntax:

• Replace aura:component with LWC template syntax.
• Use standard HTML tags and Lightning Base Components.
• Update expressions to use curly braces {} instead of !.
• Remove Aura-specific tags like aura:if, aura:iteration, and use LWC equivalents.

Aura Markup Example

<aura:component>
    <aura:attribute name="message" type="String" default="Hello, World!" />
    <lightning:button label="Click Me" onclick="{! c.handleClick }" />
    <aura:if isTrue="{! v.showMessage }">
        <p>{! v.message }</p>
    </aura:if>
</aura:component>

Converted LWC Template

<template>
    <lightning-button label="Click Me" onclick={handleClick}></lightning-button>
    <template if:true={showMessage}>
        <p>{message}</p>
    </template>
</template>

Step 5: Convert the JavaScript Controller and Helper

In LWC, the JavaScript file combines the functionality of the Aura controller and helper.

Aura Controller Example

({
    handleClick : function(component, event, helper) {
        helper.toggleMessage(component);
    }
})

Aura Helper Example

({
    toggleMessage : function(component) {
        var showMessage = component.get("v.showMessage");
        component.set("v.showMessage", !showMessage);
    }
})

Converted LWC JavaScript File

import { LightningElement, track } from 'lwc';

export default class MyComponent extends LightningElement {
    @track showMessage = false;
    message = 'Hello, World!';

    handleClick() {
        this.showMessage = !this.showMessage;
    }
}

Step 6: Handle Attributes and Properties

In Aura, attributes are defined using aura:attribute. In LWC, you define properties in the JavaScript class.

Aura Attribute Definition

<aura:attribute name="message" type="String" default="Hello, World!" />

LWC Property Definition

message = 'Hello, World!';

To make a property public (accessible from parent components), use the @api decorator:

import { LightningElement, api } from 'lwc';

export default class MyComponent extends LightningElement {
    @api message = 'Hello, World!';
}

Step 7: Convert Event Handling

Aura components use application and component events. LWC uses standard DOM events and custom events.

Aura Event Example

// Component markup
<lightning:button label="Save" onclick="{! c.handleSave }" />

// Controller
({
    handleSave : function(component, event, helper) {
        var saveEvent = component.getEvent("saveRecord");
        saveEvent.fire();
    }
})

LWC Event Example

In LWC, you create and dispatch events using the CustomEvent interface.

// Component JavaScript
handleSave() {
    const saveEvent = new CustomEvent('saverecord');
    this.dispatchEvent(saveEvent);
}

// Component Markup
<lightning-button label="Save" onclick={handleSave}></lightning-button>

The parent component can listen to the event using the lowercase event name:

<c-my-component onserverecord={handleSaveRecord}></c-my-component>

Step 8: Handle Apex Controller Calls

In Aura, you use component.get("c.methodName") to call Apex methods. In LWC, you import Apex methods and use them with wire service or imperative calls.

Aura Apex Call Example

// Controller
({
    doInit : function(component, event, helper) {
        var action = component.get("c.getAccounts");
        action.setCallback(this, function(response) {
            var state = response.getState();
            if (state === "SUCCESS") {
                component.set("v.accounts", response.getReturnValue());
            }
        });
        $A.enqueueAction(action);
    }
})

LWC Apex Call Example

First, import the Apex method:

import getAccounts from '@salesforce/apex/AccountController.getAccounts';

Then, use it with the wire service:

import { LightningElement, wire } from 'lwc';
import getAccounts from '@salesforce/apex/AccountController.getAccounts';

export default class MyComponent extends LightningElement {
    @track accounts;

    @wire(getAccounts)
    wiredAccounts({ error, data }) {
        if (data) {
            this.accounts = data;
        } else if (error) {
            // Handle error
        }
    }
}

Step 9: Convert CSS Styles

Move styles from the Aura component’s .css file to the LWC component’s .css file.

• LWC styles are encapsulated using the Shadow DOM.
• Global styles can be applied using :host and :host() selectors.
• Use SLDS classes whenever possible.

Step 10: Update Metadata Configuration

Ensure the .js-meta.xml file reflects the appropriate targets and configurations.

<?xml version="1.0" encoding="UTF-8"?>
<LightningComponentBundle xmlns="http://soap.sforce.com/2006/04/metadata">
    <apiVersion>57.0</apiVersion>
    <isExposed>true</isExposed>
    <targets>
        <target>lightning__AppPage</target>
        <target>lightning__RecordPage</target>
        <target>lightning__HomePage</target>
    </targets>
</LightningComponentBundle>

Best Practices for Converting to LWC

• Leverage Base Components: Use Lightning Base Components instead of custom components whenever possible.
• Use @track and @api Appropriately: Understand when to use decorators for reactivity and component communication.
• Avoid Deprecated Features: LWC does not support certain Aura features like two-way data binding.
• Refactor Logic: Take the opportunity to refactor and optimize code during the conversion.
• Test Thoroughly: Ensure the converted component functions correctly with unit tests and user acceptance testing.

Common Challenges and Solutions

Challenge 1: Handling Two-Way Data Binding

Solution: Implement getter and setter functions, and use events to notify parent components of changes.

Challenge 2: Replacing Aura Events

Solution: Use custom DOM events and ensure event names are in lowercase when dispatching and handling.

Challenge 3: Accessing DOM Elements

Solution: Use template.querySelector or template.querySelectorAll, and use template.refs with data- attributes.

Challenge 4: Lifecycle Hooks

Solution: Understand and use LWC lifecycle hooks like connectedCallback and renderedCallback.

Conclusion

Converting Aura components to Lightning Web Components is a valuable endeavor that modernizes your Salesforce applications and leverages the benefits of web standards. By systematically analyzing and mapping Aura features to LWC equivalents, Salesforce professionals can efficiently transition to this powerful framework. Remember to test thoroughly and take advantage of LWC’s performance and developer experience improvements.

Embracing LWC not only future-proofs your applications but also enhances scalability and maintainability, positioning your solutions at the forefront of Salesforce development.