Share JavaScript Code Between LWC and Aura

To share JavaScript code between Lightning web components and Aura components, put the code in an ES6 module.

To share an ES6 module:

• Create an ES6 module using the Lightning Web Components programming model.
• To use the code in a Lightning web component, import and reference it in the component’s JavaScript file.
• To use the code in an Aura component, use the same syntax that you use to import an Aura component and call its methods.

Create a .js file, example: extendableJS

const calculateMonthlyPayment = (principal, years, rate) => { if (principal && years && rate && rate > 0) { const monthlyRate = rate / 100 / 12; const monthlyPayment = (principal * monthlyRate) / (1 - Math.pow(1 / (1 + monthlyRate), years * 12)); return monthlyPayment; } return 0; }; export { calculateMonthlyPayment };

•Create a lwc which can use your .js functions, example: applicationTest

        import { LightningElement, track} from 'lwc'; import { getTermOptions, calculateMonthlyPayment } from 'c/extendableJS'; export default class ApplicationTest extends LightningElement { @track principal = 200000; @track term = 30; @track rate = 4; @track monthlyPayment = ''; calculateMonthlyPayment() { this.monthlyPayment = calculateMonthlyPayment( this.principal, this.term, this.rate ); }

•Create a Aura Component which can use same .js functions, 

example: auraDomListener

<aura:attribute name="termOptions" type="List"/> <aura:attribute name="principal" type="integer" default="1000"/> <aura:attribute name="term" type="integer"/> <aura:attribute name="rate" type="integer" default="10"/> <aura:attribute name="monthlyPayment" type="integer" default=""/> <c:extendableJS aura:id="pubsub" />

     calculateMonthlyPayment:function(component, event){ var pubsub = component.find('pubsub'); var calResult = pubsub.calculateMonthlyPayment(component.get("v.principal"), component.get("v.term"),component.get("v.rate")); component.set("v.monthlyPayment",calResult); }