Author: John Au-Yeung

Sometimes, we want to use getters or setters in interface definition with TypeScript.

In this article, we’ll look at how to use getters or setters in interface definition with TypeScript.

How to use getters or setters in interface definition with TypeScript?

To use getters or setters in interface definition with TypeScript, we can implement an interface property with a class with getters and setters.

For instance, we write

interface IExample {
  name: string;
}

class Example implements IExample {
  private _name: string = "jane";

  public get name() {
    return this._name;
  }

  public set name(value) {
    this._name = value;
  }
}

const example = new Example();

to create the Example class that implements the IExample interface.

In it, we have the name getter and setter which gets and sets the value of the _name instance variable respectively.

We defined the getter with get and the setter with set.

Conclusion

To use getters or setters in interface definition with TypeScript, we can implement an interface property with a class with getters and setters.

Sometimes, we want to create an async constructor functions in TypeScript.

In this article, we’ll look at how to create an async constructor functions in TypeScript.

How to create an async constructor functions in TypeScript?

To create an async constructor functions in TypeScript, we can create a factory method.

For instance, we write

class MyClass {
  private mMember: Something;

  private constructor() {}

  public static CreateAsync = async () => {
    const me = new MyClass();
    me.mMember = await SomeFunctionAsync();
    return me;
  };
}

to create the MyClass class that has a private constructor.

We use it to create a MyClass instance inside the CreateAsync function.

The function is static so we don’t need to instantiate MyClass to call it.

We return me which is the resolve value of the promise returned by CreateAsync.

Then we can use it by writing

const m = await MyClass.CreateAsync();

in an async function.

Conclusion

To create an async constructor functions in TypeScript, we can create a factory method.

Sometimes, we want to use TypeScript with native ES6 Promises.

In this article, we’ll look at how to use TypeScript with native ES6 Promises.

How to use TypeScript with native ES6 Promises?

To use TypeScript with native ES6 Promises, we can use the Promise constructor.

For instance, we write

const p = new Promise<string>((resolve, reject) => {
  resolve("a string");
});

to create a new Promise instance.

We specify that the promise resolves to a string value with <string>.

And we call resolve with a string to make the promise resolve to a string value.

Conclusion

To use TypeScript with native ES6 Promises, we can use the Promise constructor.

Sometimes, we want to check for undefined in Typescript.

In this article, we’ll look at how to check for undefined in Typescript.

How to check for undefined in Typescript?

To check for undefined in Typescript, we can use the === operator.

For instance, we write

if (email === undefined) {
}

to check if the email variable is undefined.

Conclusion

To check for undefined in Typescript, we can use the === operator.

Sometimes, we want to fix the "An async function or method in ES5/ES3 requires the ‘Promise’ constructor" with TypeScript.

In this article, we’ll look at how to fix the "An async function or method in ES5/ES3 requires the ‘Promise’ constructor" with TypeScript.

How to fix the "An async function or method in ES5/ES3 requires the ‘Promise’ constructor" with TypeScript?

To fix the "An async function or method in ES5/ES3 requires the ‘Promise’ constructor" with TypeScript, we can add the 'es2015' into the compilerOptions.lib array.

For instance, we write

{
  //...
  "compilerOptions": {
    "lib": ["es2015"]
  }
  //...
}

to set compilerOptions.lib to ["es2015"] so that the TypeScript compiler can assume that the Promise constructor is available globally in our project.

Conclusion

To fix the "An async function or method in ES5/ES3 requires the ‘Promise’ constructor" with TypeScript, we can add the 'es2015' into the compilerOptions.lib array.