That’s property spread notation. It was added in ES2018 (spread for arrays/iterables was earlier, ES2015), but it’s been supported in React projects for a long time via transpilation (as “JSX spread attributes” even though you could do it elsewhere, too, not just attributes). {…this.props} spreads out the “own” enumerable properties in props as discrete properties … Read more
In your example given, there is essentially no difference between the two .concat is significantly more efficient: http://jsperf.com/spread-into-array-vs-concat because … (spread) is merely syntax sugar on top of more fundamental underlying syntax that explicitly iterates over indexes to expand the array. Spread allows sugared syntax on top of more clunky direct array manipulation To expand … Read more
It’s not an operator. In all senses of the word, it’s not one. It has been a huge misconception since it was introduced and despite popular opinion — it’s not one, and there are a few objective points to be made: It doesn’t fit the definition of an operator It can’t be used as an … Read more
That’s property spread notation. It was added in ES2018 (spread for arrays/iterables was earlier, ES2015), but it’s been supported in React projects for a long time via transpilation (as “JSX spread attributes” even though you could do it elsewhere, too, not just attributes). {…this.props} spreads out the “own” enumerable properties in props as discrete properties … Read more
The term “spread operator” is kind of an “umbrella term” that refers to various syntactic constructs in ES6 which all look like …x. MDN does the same. However, this is misguiding, because … is not an operator (at least not in the sense the ECMAScript spec uses the term “operator”). It doesn’t generate a value … Read more
How to deep merge instead of shallow merge?