ES6：无法在调用构造函数中解构

Question

我正在尝试在 class 构造函数中使用 ES6 解构，但出现未知标记错误。这是一个例子：

// imports/server/a-and-b.js

class A {
  constructor(id) {
    // make MongoDB call and store inside this variable
    let {
      firstName: this._FirstName // => Throws here
    } = CollectionName.findOne({userId: id});
  }
}

export class B extends A {
  constructor(id) {
    super(id);
  }
  get FirstName() {
    return this._FirstName;
  }
}

// imports/server/test.js

import { B } from 'imports/server/a-and-b.js'

const b = new B('123')

const FirstName = b.FirstName;

同样的解构将在 class 之外工作：

//另一个-test.js

// make MongoDB call and store inside this variable
let {
  firstName: FirstName // works fine
} = CollectionName.findOne({userId: id});

Answer 1

您的语法不正确。你想做的事是不可能的。假设 findOne 方法是同步的，您需要这样做：

constructor(id) {
    // make MongoDB call and store inside this variable
    let { firstName } = CollectionName.findOne({userId: id});
    this._FirstName = firstName;
  }

Answer 2

我发现可以这样做：

constructor(id) {
  // make MongoDB call and store inside this variable
  ({ firstName: this._FirstName } = CollectionName.findOne({userId: id}));
}

ES6：无法在调用构造函数中解构

ES6: Can't Deconstruct inside a call constructor

javascript

ecmascript-6

javascript-objects

object-literal

es6-class