CODEWITHSUNDEEP
javascripttypescript
user2685879
user2685879

Reputation:

Typescript property does not exist on type {}

I have the following code in Typescript. Why does the compiler throws an error?

var object = {};
Object.defineProperty(object, 'first', {
     value: 37,
     writable: false,
     enumerable: true,
     configurable: true
});
console.log('first property: ' + object.first);

js.ts(14,42): error TS2339: Property 'first' does not exist on type '{}'.

It's the same code snippet like in the documentation of mozilla (examples section).

Upvotes: 12

Views: 39098

Answers (3)

Emmanuel Osimosu
Emmanuel Osimosu

Reputation: 6004

Make the object type any:

var object: any = {};

Upvotes: 7

Vayrex
Vayrex

Reputation: 1467

Another way is to do interface, so compiler will know that property exists.

interface IFirst{
  first:number;
}


let object = {} as IFirst;
Object.defineProperty(object, 'first', {
  value: 37,
  writable: false,
  enumerable: true,
  configurable: true
});
console.log('first property: ' + object.first);

Take a look at this question How to customize properties in TypeScript

Upvotes: 9

Suren Srapyan
Suren Srapyan

Reputation: 68635

That's because Typescript is a strict type language. When you create a variable and give to it a type, you can't access properties that does not exists in that type. After adding extra property will not force the compiler to look for it. If you need to add a property after the creation, make the type of your variable any.

Upvotes: 0

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