Category: JavaScript

Sometimes, we want to make web workers with TypeScript and Webpack.

In this article, we’ll look at how to make web workers with TypeScript and Webpack.

How to make web workers with TypeScript and Webpack?

To make web workers with TypeScript and Webpack, we add 'webworker' to compilerOptions.lib in tsconfig.json.

For instance, we write

{
  "compilerOptions": {
    "target": "es5",
    "lib": ["webworker", "es5", "scripthost"]
  }
}

to add 'webworker' into compilerOptions.lib in tsconfig.json.

This will let the TypeScript compiler know that we can use web worker global variables in our project.

Conclusion

To make web workers with TypeScript and Webpack, we add 'webworker' to compilerOptions.lib in tsconfig.json.

Sometimes, we want to stub a Typescript-interface or type definition.

In this article, we’ll look at how to stub a Typescript-interface or type definition.

How to stub a Typescript-interface or type definition?

To stub a Typescript-interface or type definition, we can use the typemoq library.

For instance, we write

import * as TypeMoq from "typemoq";
//...
let mock = TypeMoq.Mock.ofType<IDependency>();

mock.setup((x) => x.b()).returns(() => "Hello World");

expect(mock.object.a()).to.eq(undefined);
expect(mock.object.b()).to.eq("Hello World");

to import TypeMoq from typemoq.

Then we use TypeMoq.Mock.ofType<IDependency> to create a mocked type from the IDependency type.

And then we can use the mock with the content in IDependency without errors.

Conclusion

To stub a Typescript-interface or type definition, we can use the typemoq library.

Sometimes, we want to fix the "A const enum member can only be accessed using a string literal." error with TypeScript.

In this article, we’ll look at how to fix the "A const enum member can only be accessed using a string literal." error with TypeScript.

How to fix the "A const enum member can only be accessed using a string literal." error with TypeScript?

To fix the "A const enum member can only be accessed using a string literal." error with TypeScript, we should remove const before the enum definition.

For instance, instead of writing

const enum Snack {
  Apple = 0,
  Banana = 1,
  Orange = 2,
  Other = 3,
}

we write

enum Snack {
  Apple = 0,
  Banana = 1,
  Orange = 2,
  Other = 3,
}

Conclusion

To fix the "A const enum member can only be accessed using a string literal." error with TypeScript, we should remove const before the enum definition.

To extend a component with additional properties with React and TypeScript, we can create our own interface.

For instance, we write

export interface AnimalTableProps extends DataTableProps {
  onClickFunction: Function;
}

export class DataTable<T extends DataTableProps> extends React.Component<
  T,
  {}
> {}

export class AnimalTable extends DataTable<AnimalTableProps> {
  render() {
    //...
  }
}

to create the AnimalTableProps interface.

Then we use that as the argument for DataTable assuming it’s a generic type.

And then we can use the properties listed in AnimalTableProps and DataTableProps without compiler errors.

Sometimes, we want to transpile TypeScript to ES6.

In this article, we’ll look at how to transpile TypeScript to ES6.

How to transpile TypeScript to ES6?

To transpile TypeScript to ES6, we can set the compilerOptions.target option to 'es2015' in tsconfig.json.

For instance, we write

{
  "compilerOptions": {
    "target": "es2015"
  }
}

into tsconfig.json to make the TypeScript compiler build our code to ES6 JavaScript code.

Conclusion

To transpile TypeScript to ES6, we can set the compilerOptions.target option to 'es2015' in tsconfig.json.