What is the name of the … operator?

问题:

Is the ... operator the "spread" operator that has a two different semantics depending on its lexical position (parameter position vs destructuring assignment, Arrays, argument position etc)?

Or does it have two names "spread" and "rest"?

回答1:

It's the same operator with different names based on the usage.

Rest Properties

Rest properties collect the remaining own enumerable property keys that are not already picked off by the destructuring pattern. Those keys and their values are copied onto a new object.

let { x, y, ...z } = { x: 1, y: 2, a: 3, b: 4 };
x; // 1
y; // 2
z; // { a: 3, b: 4 }

Spread Properties

Spread properties in object initializers copies own enumerable properties from a provided object onto the newly created object.

let n = { x, y, ...z };
n; // { x: 1, y: 2, a: 3, b: 4 }

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