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How to add the className prop to a component with React and TypeScript?

To add the className prop to a component with React and TypeScript, we can add the React.HTMLAttributes type into our prop type.

For instance, we write

class MyComponent extends React.Component<
  MyProps & React.HTMLAttributes<HTMLDivElement>,
  {}
> {
  render() {
    return <div className={this.props.className}>My Div</div>;
  }
}

to set the prop type of MyComponent to MyProps & React.HTMLAttributes<HTMLDivElement>.

MyProps & React.HTMLAttributes<HTMLDivElement> is an intersection of the MyProps and React.HTMLAttributes<HTMLDivElement> types.

So the props that are in both types would be allowed in the combined types.

React.HTMLAttributes<HTMLDivElement> has the valid attributes of a div element as its properties, which includes className.

Conclusion

To add the className prop to a component with React and TypeScript, we can add the React.HTMLAttributes type into our prop type.

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How to add global types in TypeScript?

Sometimes, we want to add global types in TypeScript.

In this article, we’ll look at how to add global types in TypeScript.

How to add global types in TypeScript?

To add global types in TypeScript, we can add the declare global statement in a .d.ts file.

For instance, we write

declare global {
  interface String {
    fancyFormat(opts: StringFormatOptions): string;
  }
}

to add the String interface into the global type declaration to add the fancyFormat method to a string object.

We specify the signature of it with (opts: StringFormatOptions) and we specify that it returns a string.

Conclusion

To add global types in TypeScript, we can add the declare global statement in a .d.ts file.

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How to fix the “declaration or statement expected” error when exporting a function with TypeScript?

Sometimes, we want to fix the "declaration or statement expected" error when exporting a function with TypeScript.

In this article, we’ll look at how to fix the "declaration or statement expected" error when exporting a function with TypeScript.

How to fix the "declaration or statement expected" error when exporting a function with TypeScript?

To fix the "declaration or statement expected" error when exporting a function with TypeScript, we can use the export keyword.

For instance, we write

const myfunction = () => {
  //...
};

export { myfunction };

to define the myFunction function and export it with export.

Conlusion

To fix the "declaration or statement expected" error when exporting a function with TypeScript, we can use the export keyword.

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How to fix ‘property mock does not exist on type’ error with Jest and TypeScript?

Sometimes, we want to fix ‘property mock does not exist on type’ error with Jest and TypeScript.

In this article, we’ll look at how to fix ‘property mock does not exist on type’ error with Jest and TypeScript.

How to fix ‘property mock does not exist on type’ error with Jest and TypeScript?

To fix ‘property mock does not exist on type’ error with Jest and TypeScript, we can cast the variable with the error to the jest.MockedFunction<typeof addListener> type.

For instance, we write

const addListenerMock = addListener as jest.MockedFunction<typeof addListener>;

to cast the type with as.

Conclusion

To fix ‘property mock does not exist on type’ error with Jest and TypeScript, we can cast the variable with the error to the jest.MockedFunction<typeof addListener> type.

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How to specify generic object type in TypeScript?

Sometimes, we want to specify generic object type in TypeScript.

In this article, we’ll look at how to specify generic object type in TypeScript.

How to specify generic object type in TypeScript?

To specify generic object type in TypeScript, we can use the Record type.

For instance, we write

const myObj: Record<string, any> = {
  //...
};

to set myObj to the Record type with string keys and any type for the property values.

Conclusion

To specify generic object type in TypeScript, we can use the Record type.