Lightning Web Component OnLoad

lWCOnLoad.html:

<template>
    <div class="slds-text-heading_large slds-text-align_center">
        {greeting}
</div>
</template>

lWCOnLoad.js:

import { LightningElement, track } from 'lwc';

export default class LWCOnLoad extends LightningElement {

    @track greeting;

    connectedCallback(){
        this.greeting ='Welcome to LWC';
    }

}