Shorthand object initializer syntax for matching property name

Question

Sometimes I find myself needing to initialize an object with a property that matches the property of another object. When the property name is the same, I want to be able to use shorthand syntax.

(For the purposes of the examples in this question, I'll just keep the additional properties to a tag: 1 property, and I'll reuse message in subsequent examples as the input/source of the information. I also indicate an extra unwanted property of message because I'm cherry-picking properties and do not intend to just use Object.assign to assign all the properties of message to the result.)

const message = {
  person: {
    name: 'John'
  },
  unwanted: 'x'
};

let result = { person: message.person, tag: 1 };  // Looking for shorthand for this

To formulate the result object above, I needed to type person twice. I was thinking there must be a shorthand way to do this. My reasoning for expecting this to work is that features exist like ES2015 Shorthand property names and Destructuring assignment. e.g:

const { person } = message;  // destructing assignment
let result = { person, tag: 1 };  // shorthand property name for `person`

This would create an extra variable called person that has the value of message.person, And the result would have a property called person that has the desired value. But if there's no variable already existing then I don't know how to use shorthand in this case. And I haven't found a way to apply these two syntactical features together.

This was my first intuitive guess at what the syntax would be:

// hoping destructuring assignment is allowed in object literal
let result = { {person} = message, tag: 1 };  // it is not legal :(

My second guess was this:

// hoping that a property name would magically be inferred from `person`
let result = { message.person, tag: 1 };  // it is not legal :(

As a last resort I tried Object.assign, but it copies unwanted properties and does not cherry-pick just the person property of message.

let result = Object.assign({ tag: 1 }, message);  // Assigns unwanted properties :(

So the best I have so far is { person: message.person, tag: 1 }

Is there shorthand initializer syntax to achieve this?

Answer 1

The best I have so far is { person: message.person, tag: 1 }.

Is there shorthand initializer syntax to achieve this?

No, this is still they way to go.

hoping that a property name would magically be inferred from person

let result = { message.person, tag: 1 };

There is the ECMAScript Shorthand Property Assignment Improvements proposal that would allow exactly this. Unfortunately, it's still at stage 0 :-/