NodeJS SyntaxError: Unexpected token . How can I try to fix?

I am very new in NodeJS and I have the following problem running a node application:

andrea@ubuntu:~/Documents/XXX/custom-dashboard-be$ npm run dev

> custom-dashboard-be@1.6.0 dev /home/andrea/Documents/XXX/custom-dashboard-be
> cross-env NODE_ENV=development nodemon src/index.js

[nodemon] 2.0.7
[nodemon] to restart at any time, enter `rs`
[nodemon] watching path(s): *.*
[nodemon] watching extensions: js,mjs,json
[nodemon] starting `node src/index.js`
/home/andrea/Documents/XXX/custom-dashboard-be/src/utils/esMapper.js:29
    if(data.result && data.result.body && data.result.body?.aggregations["2"]?.buckets.length > 0) {
                                                           ^

SyntaxError: Unexpected token .
    at Module._compile (internal/modules/cjs/loader.js:723:23)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)
    at Module.load (internal/modules/cjs/loader.js:653:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:593:12)
    at Function.Module._load (internal/modules/cjs/loader.js:585:3)
    at Module.require (internal/modules/cjs/loader.js:692:17)
    at require (internal/modules/cjs/helpers.js:25:18)
    at Object.<anonymous> (/home/andrea/Documents/XXX/custom-dashboard-be/src/controllers/elastic.controller.js:5:109)
    at Module._compile (internal/modules/cjs/loader.js:778:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)
[nodemon] app crashed - waiting for file changes before starting...

The error seems on the line 29 of this esMapper.js class, that is the first if statment of this method:

const esSudoEventsAndHostnamesMapper = async (data) => {

    if(data.result && data.result.body && data.result.body?.aggregations["2"]?.buckets.length > 0) {
        let aggregations = data.result.body.aggregations["2"].buckets;

        aggregations.map((event) => {
            let totalCount = event.doc_count;
            event["3"].buckets.map(nestedEvent => {
                nestedEvent.percentage = ((nestedEvent.doc_count / totalCount) * 100).toFixed(2);
            })
        })

        data.result.body.aggregations["2"].buckets = aggregations;
    }
    return data;
}

Why? How can I try to fix this issue?

Your problem seems to be using optional chaining operator in an unsupported node version which is likely (<14). Keep in mind that only node 14 and later can support this.

But as I know that you can use the option (--harmony) to enable some new features but I haven't yet tested before.

In short, the solution is either to update your node version >=14 or try to use node --harmony src/index.js.