CODEWITHSUNDEEP
javascript
Jordi
Jordi

Reputation: 23207

Typescript: Merge objects created by Object.defineProperty

I've an array like this:

let aa = [
    Object.defineProperty({alignedType: "t"}, "f1", {value: 1}),
    Object.defineProperty({alignedType: "t"}, "f2", {value: 2}),
    Object.defineProperty({alignedType: "t"}, "f3", {value: 3}),
    Object.defineProperty({alignedType: "t"}, "f4", {value: 4})
];

I need to reduce this array an simple object like:

let yyy = aa.reduce((acc, e) => {
    return {...acc, ...e};
});

I'm running against yyy only contains a single object with only alignedType: "t". It has no more properties.

Here you have debugger:

enter image description here

The object I was expecting is: {alignedType: "t", f1: 1, f2: 2, f3: 3, f4: 4}.

Any ideas?

Upvotes: 0

Views: 95

Answers (1)

Maxim Pyshko
Maxim Pyshko

Reputation: 580

You need to set { enumerable: true } to say that this property shows up during enumeration of the properties on the corresponding object:

let aa = [
  Object.defineProperty({ alignedType: 't' }, 'f1', { value: 1, enumerable: true }),
  Object.defineProperty({ alignedType: 't' }, 'f2', { value: 1, enumerable: true }),
  Object.defineProperty({ alignedType: 't' }, 'f3', { value: 1, enumerable: true }),
  Object.defineProperty({ alignedType: 't' }, 'f4', { value: 1, enumerable: true }),
];


let yyy = aa.reduce((acc, e) => {
  return {...acc, ...e};
});

console.log(yyy);

See enumerable on developer.mozilla.org

Update

From https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax:

The Rest/Spread Properties for ECMAScript proposal (stage 4) adds spread properties to object literals. It copies own enumerable properties from a provided object onto a new object.

Upvotes: 1

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