Category: TypeScript

Sometimes, we want to convert a set to an array in TypeScript.

In this article, we’ll look at how to convert a set to an array in TypeScript.

How to convert a set to an array in TypeScript?

To convert a set to an array in TypeScript, we can set the downlevelIteration option to true in tsconfig.json‘s compilerOptions.

Then we can use the spread operator to convert sets to arrays.

For instance, we write

{
  "compilerOptions": {
    "downlevelIteration": true
  }
}

to set the downlevelIteration option to true in our project.

Then we can use the spread operator on a set by writing

const arr = [...set];

to convert it to an array.

Conclusion

To convert a set to an array in TypeScript, we can set the downlevelIteration option to true in tsconfig.json‘s compilerOptions.

Then we can use the spread operator to convert sets to arrays.

Sometimes, we want to initialize an object in TypeScript.

In this article, we’ll look at how to initialize an object in TypeScript.

How to initialize an object in TypeScript?

To initialize an object in TypeScript, we can create an object that matches the properties and types specified in the interface.

For instance, we write

export interface Category {
  name: string;
  description: string;
}

const category: Category = {
  name: "My Category",
  description: "My Description",
};

to create the Category interface with the name and description string properties.

Then we create the category Category variable which has the same properties set to strings so that the properties and types matches the interface exactly.

We can also make the properties optional by putting ? after the property name, so we write

export interface Category {
  name?: string;
  description?: string;
}

to make name and description optional.

Conclusion

To initialize an object in TypeScript, we can create an object that matches the properties and types specified in the interface.

Sometimes, we want to add multiple type signatures for members or union types in TypeScript.

In this article, we’ll look at how to add multiple type signatures for members or union types in TypeScript.

How to add multiple type signatures for members or union types in TypeScript?

To add multiple type signatures for members or union types in TypeScript, we can add union types with TypeScript.

For instance, we write

interface Foo {
  bar: string | boolean;
}

to set the bar property to be either a string or boolean with string | boolean.

Conclusion

To add multiple type signatures for members or union types in TypeScript, we can add union types with TypeScript.

To extend TypeScript global object in Node.js, we can add a type definition file that extends the Global interface in the NodeJS module.

For instance, we write

declare module NodeJS {
  interface Global {
    foo: any;
  }
}

in a .d.ts file in our Node TypeScript project to add the foo property into the Global interface.

Then we can use the variable without compiler errors by using global.foo.

Conclusion

To extend TypeScript global object in Node.js, we can add a type definition file that extends the Global interface in the NodeJS module.

Sometimes, we want to define a private property when implementing an interface in TypeScript.

In this article, we’ll look at how to define a private property when implementing an interface in TypeScript.

How to define a private property when implementing an interface in TypeScript?

To define a private property when implementing an interface in TypeScript, we can add private properties into the class that implements the interface.

For instance, we write

interface IModuleMenuItem {
  getName(): string;
}

class ModuleMenuItem implements IModuleMenuItem {
  private name;

  public getName() {
    return name;
  }

  protected setName(newName: string) {
    name = newName;
  }
}

to add the name private variable into the ModuleMenuItem class.

All interface properties must be public.

Conclusion

To define a private property when implementing an interface in TypeScript, we can add private properties into the class that implements the interface.