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Object.keys for a non-instantiated object interface type

Enforcing the type of the indexed members of a Typescript object?Interface type check with TypescriptTypescript interface default valuesTypescript: Interfaces vs TypesTypescript type mapping to expect an object where every property is of a given typeExtending Non Generic Interface with Generic InterfaceTypescript - Force default type for additional properties in interfaceInstantiating an exported TypeScript interfaceDefining an interface for an object which is extended by another interfaceUse an enum to type an index signature of an interface field?

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0

Is there a way to use Object.keys on an interface type itself to get all of the properties of that object type?

export interface Apple
 id: number;
 name: string;
 status: string;


Object.keys(Apple)

Exepected output would be ["id", "name", "status"] like the normal Object.keys. I can't seem to find a way or documentation to accomplish this.

typescript

share|improve this question

asked Mar 28 at 21:38

C.ProgrammingC.Programming

3877 bronze badges

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  As Sam Herrmann mentioned, it sounds impossible. Why do you want to do this?
  
  – Dakota Jang
  Mar 28 at 21:47
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I wanted to set a constant at the top of my file that has all the properties of the interface. I iterate through them for the diffing tool I am writing, so I wanted to keep them dynamic in case any properties got added or deleted.
  
  – C.Programming
  Mar 28 at 21:52
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Isn't that the reason why we use Typescript? class Foo implements Bar would complain if Foo is missing some implementations in Bar. If you want to prevent modification in runtime, you could try Object.freeze. Though I have a feeling that's not exactly something you are looking for.
  
  – Dakota Jang
  Mar 31 at 2:08
  

  
  
  
  

add a comment
 | 

0

Is there a way to use Object.keys on an interface type itself to get all of the properties of that object type?

export interface Apple
 id: number;
 name: string;
 status: string;


Object.keys(Apple)

Exepected output would be ["id", "name", "status"] like the normal Object.keys. I can't seem to find a way or documentation to accomplish this.

typescript

share|improve this question

asked Mar 28 at 21:38

C.ProgrammingC.Programming

3877 bronze badges

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  As Sam Herrmann mentioned, it sounds impossible. Why do you want to do this?
  
  – Dakota Jang
  Mar 28 at 21:47
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I wanted to set a constant at the top of my file that has all the properties of the interface. I iterate through them for the diffing tool I am writing, so I wanted to keep them dynamic in case any properties got added or deleted.
  
  – C.Programming
  Mar 28 at 21:52
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Isn't that the reason why we use Typescript? class Foo implements Bar would complain if Foo is missing some implementations in Bar. If you want to prevent modification in runtime, you could try Object.freeze. Though I have a feeling that's not exactly something you are looking for.
  
  – Dakota Jang
  Mar 31 at 2:08
  

  
  
  
  

add a comment
 | 

Is there a way to use Object.keys on an interface type itself to get all of the properties of that object type?

export interface Apple
 id: number;
 name: string;
 status: string;


Object.keys(Apple)

Exepected output would be ["id", "name", "status"] like the normal Object.keys. I can't seem to find a way or documentation to accomplish this.

typescript

share|improve this question

asked Mar 28 at 21:38

C.ProgrammingC.Programming

3877 bronze badges

export interface Apple
 id: number;
 name: string;
 status: string;


Object.keys(Apple)

share|improve this question

asked Mar 28 at 21:38

C.ProgrammingC.Programming

3877 bronze badges

share|improve this question

asked Mar 28 at 21:38

C.ProgrammingC.Programming

3877 bronze badges

asked Mar 28 at 21:38

C.ProgrammingC.Programming

3877 bronze badges

asked Mar 28 at 21:38

C.ProgrammingC.Programming

3877 bronze badges

2 Answers
2

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2

This is not possible because TypeScript is only present at development time. Once your code is transpiled to JavaScript, there is no way to reference back to TypeScript types at runtime.

share|improve this answer

answered Mar 28 at 21:42

Sam HerrmannSam Herrmann

2,0421010 silver badges2626 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  That's a bummer. But makes sense. I guess I will have to hardcode the property names and just update it manually if there are any changes. Thank you!
  
  – C.Programming
  Mar 28 at 21:52
  

  
  
  
  

add a comment
 | 

2

From documentation I see the following for return value of Object.keys():

An array of strings that represent all the enumerable properties of the given object.

Source: Object.keys().

Which means for example if you have a class what you instantiate from JavaScript then you can get the keys into an array but not from the interface (from TypeScript):

let redApple = new Apple();
let keys = Object.keys(redApple);
let classKeys = Object.keys(Apple);

console.log('keys of the instance', keys);
console.log('keys of the class', classKeys); 

function Apple() 
 this.id = '';
 this.name = '';
 this.status = '';

We should remember always that at the end TypeScript will be transpiled to JavaScript.

share|improve this answer

edited Mar 28 at 21:58

answered Mar 28 at 21:50

norbitrialnorbitrial

1,21744 silver badges1414 bronze badges

add a comment
 | 

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2

This is not possible because TypeScript is only present at development time. Once your code is transpiled to JavaScript, there is no way to reference back to TypeScript types at runtime.

share|improve this answer

answered Mar 28 at 21:42

Sam HerrmannSam Herrmann

2,0421010 silver badges2626 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  That's a bummer. But makes sense. I guess I will have to hardcode the property names and just update it manually if there are any changes. Thank you!
  
  – C.Programming
  Mar 28 at 21:52
  

  
  
  
  

add a comment
 | 

2

This is not possible because TypeScript is only present at development time. Once your code is transpiled to JavaScript, there is no way to reference back to TypeScript types at runtime.

share|improve this answer

answered Mar 28 at 21:42

Sam HerrmannSam Herrmann

2,0421010 silver badges2626 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  That's a bummer. But makes sense. I guess I will have to hardcode the property names and just update it manually if there are any changes. Thank you!
  
  – C.Programming
  Mar 28 at 21:52
  

  
  
  
  

add a comment
 | 

This is not possible because TypeScript is only present at development time. Once your code is transpiled to JavaScript, there is no way to reference back to TypeScript types at runtime.

share|improve this answer

answered Mar 28 at 21:42

Sam HerrmannSam Herrmann

2,0421010 silver badges2626 bronze badges

share|improve this answer

answered Mar 28 at 21:42

Sam HerrmannSam Herrmann

2,0421010 silver badges2626 bronze badges

answered Mar 28 at 21:42

Sam HerrmannSam Herrmann

2,0421010 silver badges2626 bronze badges

answered Mar 28 at 21:42

Sam HerrmannSam Herrmann

2,0421010 silver badges2626 bronze badges

2

From documentation I see the following for return value of Object.keys():

An array of strings that represent all the enumerable properties of the given object.

Source: Object.keys().

Which means for example if you have a class what you instantiate from JavaScript then you can get the keys into an array but not from the interface (from TypeScript):

let redApple = new Apple();
let keys = Object.keys(redApple);
let classKeys = Object.keys(Apple);

console.log('keys of the instance', keys);
console.log('keys of the class', classKeys); 

function Apple() 
 this.id = '';
 this.name = '';
 this.status = '';

We should remember always that at the end TypeScript will be transpiled to JavaScript.

share|improve this answer

edited Mar 28 at 21:58

answered Mar 28 at 21:50

norbitrialnorbitrial

1,21744 silver badges1414 bronze badges

add a comment
 | 

2

From documentation I see the following for return value of Object.keys():

An array of strings that represent all the enumerable properties of the given object.

Source: Object.keys().

Which means for example if you have a class what you instantiate from JavaScript then you can get the keys into an array but not from the interface (from TypeScript):

let redApple = new Apple();
let keys = Object.keys(redApple);
let classKeys = Object.keys(Apple);

console.log('keys of the instance', keys);
console.log('keys of the class', classKeys); 

function Apple() 
 this.id = '';
 this.name = '';
 this.status = '';

We should remember always that at the end TypeScript will be transpiled to JavaScript.

share|improve this answer

edited Mar 28 at 21:58

answered Mar 28 at 21:50

norbitrialnorbitrial

1,21744 silver badges1414 bronze badges

add a comment
 | 

From documentation I see the following for return value of Object.keys():

An array of strings that represent all the enumerable properties of the given object.

Source: Object.keys().

Which means for example if you have a class what you instantiate from JavaScript then you can get the keys into an array but not from the interface (from TypeScript):

let redApple = new Apple();
let keys = Object.keys(redApple);
let classKeys = Object.keys(Apple);

console.log('keys of the instance', keys);
console.log('keys of the class', classKeys); 

function Apple() 
 this.id = '';
 this.name = '';
 this.status = '';

We should remember always that at the end TypeScript will be transpiled to JavaScript.

share|improve this answer

edited Mar 28 at 21:58

answered Mar 28 at 21:50

norbitrialnorbitrial

1,21744 silver badges1414 bronze badges

let redApple = new Apple();
let keys = Object.keys(redApple);
let classKeys = Object.keys(Apple);

console.log('keys of the instance', keys);
console.log('keys of the class', classKeys); 

function Apple() 
 this.id = '';
 this.name = '';
 this.status = '';

let redApple = new Apple();
let keys = Object.keys(redApple);
let classKeys = Object.keys(Apple);

console.log('keys of the instance', keys);
console.log('keys of the class', classKeys); 

function Apple() 
 this.id = '';
 this.name = '';
 this.status = '';

let redApple = new Apple();
let keys = Object.keys(redApple);
let classKeys = Object.keys(Apple);

console.log('keys of the instance', keys);
console.log('keys of the class', classKeys); 

function Apple() 
 this.id = '';
 this.name = '';
 this.status = '';

share|improve this answer

edited Mar 28 at 21:58

answered Mar 28 at 21:50

norbitrialnorbitrial

1,21744 silver badges1414 bronze badges

answered Mar 28 at 21:50

norbitrialnorbitrial

1,21744 silver badges1414 bronze badges

answered Mar 28 at 21:50

norbitrialnorbitrial

1,21744 silver badges1414 bronze badges