Capturing nested levels in JavaScript destructuring [duplicate]

Does JavaScript destructuring have syntax to capture both an object and its content?

In other words, can I do the following completely in the function's arg list without the following const line?

f = (a) => {
  const {b} = a;
  console.log("I see:", a, "and", b);
}

f({b:42})

==> I see {b: 42} and 42

(FWIW: I'm thinking of something like :as in Clojure or ClojureScript).

Yes you can

const f = (a, {b} = a ) => {
  console.log("I see:", a, "and", b);
}

f({b:42})

For more use cases of destructuring assignment you can see this

On side note:- Always keep one extra parameter than you in function definition than than your function call.

Update With this way you need not to worry about one extra parameter in function definition

const f = (...z) => (a=z[0],{b}=z[0],...arguments) => {
  console.log("I see:", a, "and", b, z);
}

f({b:42},{b:32})()

You can try it with IIFE's too @bergi thanks for inputs.

const f = (a, ...z) => (({b}) => {
  console.log("I see:", a, "and", b, z);
})(a);

f({b:42},{b:32})

This is a way

const f = (a, {b}=a) => {
  console.log("I see:", a, "and", b);
}

f({b:42})

The problem comes up when you need to pass more than one parameter.

const f = (a, {b}=a) => {
  console.log("I see:", a, "and", b);
}

f({b:42},123)

来源：https://stackoverflow.com/questions/54931090/capturing-nested-levels-in-javascript-destructuring

标签