Why i have this error when run node index.js and how to fix it

Question

My code run well on browser, however when run by node index.js I get this error :

let x = (agr[item.id] ??= { id: item.id, count: 0 });
                                     ^

SyntaxError: Unexpected token '?'

This is my code

var array  = [{"id":1,"count":100},{"id":2,"count":200},{"id":1,"count":200}]
const groupedData = array.reduce((agr,item)=>{
    let x = (agr[item.id] ??= { key: item.id, count:0 });
    x.count+=(item.count);
    return agr
},{});
const result = Object.entries(groupedData).reduce((agr, item) => {
    agr.push(item);
    return agr;
}, []); 
console.log(result);

Thanks for your attention

let x = (agr[item.id] ??= { key: item.id, count:0 }); should be let x = (agr[item.id] = { key: item.id, count:0 }); — Lautre
– Lautre, Commented Jun 17, 2021 at 9:58
My code run very well on browser. The result is 1 array: [{"1","key:1,count:300"},{"2","key:2,count:200"}] — Đoàn Đức Bảo
– Đoàn Đức Bảo, Commented Jun 17, 2021 at 10:03
??= only supported in Node 15.x. developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… — ikhvjs
– ikhvjs, Commented Jun 17, 2021 at 10:10

Quentin · Accepted Answer · 2021-06-17 10:17:48Z

2

The Logical nullish assignment is a very new feature to JavaScript.

Your version of Node.js is too old to support it.

Upgrade to Node.js 15.0.0 or (preferably) newer.

edited Jun 17, 2021 at 10:17

answered Jun 17, 2021 at 10:01

Quentin

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