Lightning Web Components (LWC) is a new programming model for building modern, scalable, and high-performance web applications on the Salesforce platform. LWC is based on modern web standards and provides a developer-friendly experience for building reusable components that can be shared across an organization.
In this blog post, I will explore some best practices for building lightning web components and how to leverage the LWC programming model to build efficient and maintainable applications.
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Use Modules for Reusibility
One of the best practices for building Lightning Web Components is to use modules for reusability. Modules are JavaScript files that can be imported into other JavaScript files. By using modules, you can reuse code across different components and applications. This helps to reduce the amount of code you need to write and makes it easier to maintain your codebase.
To create a module, you can use the export keyword to export functions, variables, or classes from a file. Then, you can import the module into another file using the import keyword.
For example, suppose you have a module called utils.js that contains a utility function called formatName. You can export the function using the following code:
export function formatName(firstName, lastName) {
return `${firstName} ${lastName}`;
}To import the formatName function into another file, you can use the following code:
import { formatName } from './utils';
const fullName = formatName('John', 'Doe');
console.log(fullName); // Output: "John Doe" Use Custom Events for Communication Between Components
Another best practice for building Lightning Web Components is to use custom events for communication between components. Custom events are events that you define yourself and can be used to pass data or invoke methods in other components.
To create a custom event, you can use the CustomEvent constructor and dispatch the event using the dispatchEvent method. For example, suppose you have a component called parent-component that wants to send a message to a component called child-component. You can use the following code in parent-component to create and dispatch a custom event:
const message = { text: 'Hello, world!' };
const event = new CustomEvent('message-sent', { detail: message });
this.dispatchEvent(event);To listen for the custom event in child-component, you can use the addEventListener method. For example:
this.addEventListener('message-sent', (event) => {
const message = event.detail;
console.log(message.text); // Output: "Hello, world!"
});Use The @api Decorator to Expose Component Properties And Methods
One of the key features of LWC is the ability to easily expose component properties and methods to other components and to the parent component. This is done using the @api decorator.
For example, consider the following component:
import { LightningElement, api } from 'lwc';
export default class MyComponent extends LightningElement {
@api greeting = 'Hello';
@api
sayHello() {
console.log(this.greeting);
}
} In this example, the greeting property and the sayHello method are exposed to other components and to the parent component. To access these properties and methods from another component, you can use the @api decorator to create a public API for your component.
For example, to access the greeting property from another component, you can do the following:
import { LightningElement, api } from 'lwc';
export default class AnotherComponent extends LightningElement {
@api
get greeting() {
return this.template.querySelector('c-my-component').greeting;
}
} Use The @track Decorator to Optimize Data Binding
In LWC, data binding is used to synchronize data between a component and its template. When a component’s data changes, the template is automatically updated to reflect the new data.
To enable data binding in a component, you can use the @track decorator on properties that you want to bind to the template. The @track decorator tells LWC to observe changes to the decorated property and re-render the template whenever the property changes.
For example, consider the following component:
import { LightningElement, track } from 'lwc';
export default class MyComponent extends LightningElement {
@track name = 'John';
} In this example, the name property is decorated with the @track decorator. This means that whenever the name property changes, the template will be automatically updated to reflect the new value.
It’s important to note that the @track decorator has a performance cost, as it adds additional overhead to the component’s rendering process. Therefore, it’s best to use the @track decorator only on properties that actually need to be tracked.
Note – Starting Spring ’20 release, you don’t need to use the ‘@track’ decorator on primitives. You only need it to make an object or array reactive.
Use The @wire Decorator to Declaratively Fetch Data
The @wire decorator is a powerful tool for declaratively fetching data in Lightning Web Components (LWC). It allows you to specify a property or method in your component and have its value automatically populated with data from an Apex method or a wire adapter. This can greatly simplify your code and make it easier to keep your component in sync with your data.
To use the @wire decorator, you will need to import it from the lwc module:
import { wire } from 'lwc';Next, you can use the @wire decorator to decorate a property or method in your component:
export default class MyComponent extends LightningElement {
@wire(myApexMethod)
myProperty;
@wire(myWireAdapter)
myMethod(result) {
// do something with the result
}
} The @wire decorator takes a single argument, which can be either an Apex method or a wire adapter. An Apex method is a function that is defined in an Apex class and executed on the server. A wire adapter is a function that is defined in a JavaScript module and executed on the client.
In either case, the @wire decorator will automatically execute the specified function and store the result in the decorated property or method. If the data changes, the component will automatically re-render to reflect the new data.
Always Cache The Data
There are several ways to cache data in Lightning Web Components. Here are a few options:
Custom Cache: You can create your own custom cache to store data that you frequently use in your component. You can use a simple JavaScript object to store the data, and use the component’s
connectedCallbacklifecycle hook to check if the data is already in the cache. If it is, you can retrieve it from the cache. If it’s not, you can fetch the data and add it to the cache before rendering the component.@wire Caching: If you are using the
@wiredecorator to fetch data from an Apex method or a server-side function, you can enable caching by setting thecacheableproperty totrue. This will cause the data to be stored in a cache that is managed by the framework, and subsequent requests for the same data will be served from the cache instead of making a new server call.Browser Cache: If you are making HTTP requests to an external API or a static resource, you can leverage the browser’s cache by setting appropriate cache control headers on the server. This will cause the browser to store the data in its cache, and subsequent requests for the same data will be served from the cache until the cache expires.
Which method you choose will depend on your specific use case and the type of data you are caching.
Conditional Rendering
To perform conditional rendering in a Lightning web component, you can use an if:true|false directive in your template. For example:
<template>
<div>
<template if:true={isTrue}>
This will be rendered if isTrue is truthy.
</template>
<template if:false={isFalse}>
This will be rendered if isFalse is falsy.
</template>
</div>
</template> You can also use the if:true and if:false directives together to perform a conditional rendering based on the value of a boolean expression.
<template>
<div>
<template if:true={isTrue}>
This will be rendered if isTrue is truthy.
</template>
<template if:false={isTrue}>
This will be rendered if isTrue is falsy.
</template>
</div>
</template> You can also use the rendered attribute to conditionally render an element based on the value of a boolean expression.
<template>
<div>
<div rendered={isTrue}>
This will be rendered if isTrue is truthy.
</div>
</div>
</template> Disclaimer
This article is not endorsed by Salesforce or any other company in any way. I shared my knowledge on this topic in this blog post. Please refer to Salesforce Help for the latest information.
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