Unable to get the data in columns using lightning data table with imperative call and javascript

Question

I am new to salesforce, I am trying to learn lightning datatable with imperative call in salesforce. I am unable to get the data in the column, its not throwing any error though. Please help to fix it. Below is the code:

''' HTML Code:

<template>
    <lightning-datatable
    key-field="Id"
    data={result}
    columns={columns}></lightning-datatable>
</template>

''' Javascript:

import { LightningElement, track } from 'lwc';
import getContactList from '@salesforce/apex/ContactController.getData';

const columns = [
    { label: 'First Name', fieldName: 'FirstName' },
    //{ label: 'Last Name', fieldName: 'LastName' },
    //{ label: 'Email', fieldName: 'Email', type: 'email' },
];

export default class DataTableWithImperativeCall extends LightningElement {
    @track result=[];
    @track columns = columns;
    connectedCallback() {
        this.getResults();
    }

    getResults() {
        getContactList()
            .then(cdata => {
                //console.log(cdata);
                console.log(JSON.stringify(cdata));
                let finalData=[];
                for(var i=0;i<cdata.length;i++)
                {
                    finalData.push(cdata[i].FirstName);
                }
                this.result=finalData;
                //console.log('results'+JSON.stringify(this.result));
            })
            .catch(error => {
                this.errors = error;
            });

    }
}

''' Apex Class:

public with sharing class ContactController {
    @AuraEnabled
    public static list<contact> getData()
    {
        return [select id,firstName,LastName,email from contact order by firstName asc nulls last limit 10];
    }
}

'''

Answer 1

In LWC Datatable pushing data to array using push method does not trigger any change in UI. You will have to reassign the data to array with = operator.

let finalData = [];
for (var i = 0; i < cdata.length; i++) {
    finalData.push(cdata[i].FirstName);
}
this.result = finalData;

To know more on this please check here