Combining destructuring with parameter properties

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#5,326 109 comments 651 reactions 0 assignees View on GitHub

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
25/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
typescript
Domain
compilers

Research direction

Start by studying the parameter-property and destructuring examples in the issue, then read the 109-comment discussion for prior constraints and proposed interpretations. A complete change would need a settled syntax decision plus corresponding type-checking and transpilation behavior matching the requested output.

Written by the indexing model from the issue text.

Description

Effort: Moderate In Discussion Suggestion

Today, we can take advantage of parameter properties to reduce the boilerplate, e.g:

class Person {
  constructor(public firstName: string, public lastName: number, public age: number) {

  }
}

Since 1.5, we can also use destructuring, e.g:

class Person {
  firstName: string;
  lastName: string;
  age: number;

  constructor({ firstName, lastName, age } : { firstName: string, lastName: string, age: number }) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.age = age;
  }
}

I've tried in many ways to combine both features, but had no success. So:

  1. Is it possible to combine them nowadays, and if yes, how?
  2. If not, could it be an improvement to a future TypeScript version? E.g:
class Person {
  constructor(public { firstName, lastName, age } : { firstName: string, lastName: string, age: number }) {

  }
}

// the code above would possibly transpile to:
var Person = (function () {
    function Person(_a) {
        var firstName = _a.firstName, lastName = _a.lastName, age = _a.age;
        this.firstName = firstName;
        this.lastName = lastName;
        this.age = age;
    }
    return Person;
})();
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