Category: TypeScript

Sometimes, we want to convert TypeScript enum to object array.

In this article, we’ll look at how to convert TypeScript enum to object array.

How to convert TypeScript enum to object array?

To convert TypeScript enum to object array, we can use the Object.values method.

For instance, we write

enum Colors {
  WHITE = 0,
  BLACK = 1,
  BLUE = 3,
}

const colorValueArray = Object.values(Colors);

to create the Colors enum.

Then we call Object.values with Colors to return an array of enum values.

Conclusion

To convert TypeScript enum to object array, we can use the Object.values method.

Sometimes, we want to disable a TypeScript rule for a specific line.

In this article, we’ll look at how to disable a TypeScript rule for a specific line.

How to disable a TypeScript rule for a specific line?

To disable a TypeScript rule for a specific line, we can use the @ts-ignore comment.

For instance, we write

if (false) {
  // @ts-ignore: Unreachable code error
  console.log("hello");
}

to add the // @ts-ignore: Unreachable code error comment so that the TypeScript compiler ignores the unreachable code error in the line after the comment.

Conclusion

To disable a TypeScript rule for a specific line, we can use the @ts-ignore comment.

To fix No index signature with a parameter of type ‘string’ was found on type ‘{ "A": string; } with TypeScript, we can use the keyof operator to set the type of the key we use to access an object’s property is actually in the object.

For instance, we write

interface User {
  name: string;
  age: number;
}

const user: User = {
  name: "james",
  age: 20,
};

const getValue = (key: keyof User) => {
  return user[key];
};

to define the getValue function that takes the key parameter.

We set the key parameter to keyof User so that the value of key can only be the property keys listed in the User interface.

Then we can access the properties of user with key without compiler errors.

Sometimes, we want to get the object length in TypeScript.

In this article, we’ll look at how to get the object length in TypeScript.

How to get the object length in TypeScript?

To get the object length in TypeScript, we can use the Object.keys method and the array length property.

For instance, we write

Object.keys(customer).length;

to return an array of non-inherited keys from the customer object with Object.keys.

Then we get the length of the array with length.

Conclusion

To get the object length in TypeScript, we can use the Object.keys method and the array length property.

Sometimes, we want to add constructor overload with empty constructor in TypeScript.

In this article, we’ll look at how to add constructor overload with empty constructor in TypeScript.

How to add constructor overload with empty constructor in TypeScript?

To add constructor overload with empty constructor in TypeScript, we can add different signatures for constructor in our class.

For instance, we write

class Foo {
  constructor();
  constructor(id: number);
  constructor(id: number, name: string, surname: string, email: string);
  constructor(id?: number, name?: string, surname?: string, email?: string) {
    this.id = id;
    this.name = name;
    this.surname = surname;
    this.email = email;
  }
}

to overload constructor by adding different signatures for it.

Then we can do whatever we want with the parameters listed in any signature in the constructor body.

Conclusion

To add constructor overload with empty constructor in TypeScript, we can add different signatures for constructor in our class.