typescript , spread and object.assign

Question

I was just browsing through some typescript generated code and was somewhat surprised at the code for spread

test.ts

let task = { ...data };

test.js

let task = Object.assign({}, data);

I double-checked the tsconfig.json file and have under compilerOptions

"target": "es2017",

I thought that the spread operator was valid es6 code

So, changed the target to read

"target": "ESNext",

and my test.js now has

let task = { ...data };

I'm using typescript 2.7.2

So, basically the question boils down to why do I need EsNext instead of es2017 / es6 ?

Answer 1

The Object rest/spread properties are, unlike the Array rest/spread properties, not included in the ES2017 spec. They are however included in the ES2018 spec.