Author: John Au-Yeung

Sometimes, we want to fix TypeScript enum switch statement not working.

In this article, we’ll look at how to fix TypeScript enum switch statement not working.

How to fix TypeScript enum switch statement not working?

To fix TypeScript enum switch statement not working, we should make sure we’re comparing numbers with switch if we didn’t assign any value non-number to the enum values.

For instance, we write

enum EditMode {
  View = 0,
  Edit = 1,
  Delete = 2,
}

switch (+editMode) {
  case EditMode.Delete:
    //...
    break;
  case EditMode.Edit:
    // ...
    break;
  default:
    //...
    break;
}

to create the EditMode enum that has numbers assigned to each entry.

Then we make sure editMode is a number before doing comparisons by adding a + sign in front of it.

Then the switch statement should do the comparisons property since we’re comparing 2 numbers.

Conclusion

To fix TypeScript enum switch statement not working, we should make sure we’re comparing numbers with switch if we didn’t assign any value non-number to the enum values.

Sometimes, we want to fix the "’string’ can’t be used to index type ‘{}’" error with TypeScript.

In this article, we’ll look at how to fix the "’string’ can’t be used to index type ‘{}’" error with TypeScript.

How to fix the "’string’ can’t be used to index type ‘{}’" error with TypeScript?

To fix the "’string’ can’t be used to index type ‘{}’" error with TypeScript, we should make sure the properties and types of each property listed in the interfaces matches the ones that are in the object.

For instance, we write

interface Item {
  id: number;
  name: string;
  email: string;
}

export type TableGridViewProps = {
  items: Item[];
  tableColumns: TableColumn[];
};

to create the Item interface and the TableGridViewProps prop that has properties set to the Item[] type.

Then the items in items should have objects that have the properties listed in Item and the types of each property should also match the ones listed in Item for each property.

Conclusion

To fix the "’string’ can’t be used to index type ‘{}’" error with TypeScript, we should make sure the properties and types of each property listed in the interfaces matches the ones that are in the object.

Sometimes, we want to fix the "Cannot find name ‘console’" error with Node.js and TypeScript.

In this article, we’ll look at how to fix the "Cannot find name ‘console’" error with Node.js and TypeScript.

How to fix the "Cannot find name ‘console’" error with Node.js and TypeScript?

To fix the "Cannot find name ‘console’" error with Node.js and TypeScript, we can install the @types/node package into our Node.js project.

To install it, we run

npm install @types/node --save-dev

to add @types/node as a dev dependency.

Conclusion

To fix the "Cannot find name ‘console’" error with Node.js and TypeScript, we can install the @types/node package into our Node.js project.

Sometimes, we want to create a function interface with TypeScript.

In this article, we’ll look at how to create a function interface with TypeScript.

How to create a function interface with TypeScript?

To create a function interface with TypeScript, we can put the signature and return type of the function in an interface.

For instance, we write

interface IFormatter {
  (data: string, toUpper: boolean): string;
}

const upperCaseFormatter: IFormatter = (data: string) => {
  return data.toUpperCase();
};

to create the IFormatter interface that requires a function to have signature that some or all of the parameters in (data: string, toUpper: boolean) and returns a string.

We can then create the upperCaseFormatter function with type IFormatter and with the data string parameter and returns a string.

Conclusion

To create a function interface with TypeScript, we can put the signature and return type of the function in an interface.

Sometimes, we want to define a regex-matched string type in TypeScript.

In this article, we’ll look at how to define a regex-matched string type in TypeScript.

How to define a regex-matched string type in TypeScript?

To define a regex-matched string type in TypeScript, we can create a literal type that matches the pattern of a given string.

For instance, we write

type MarkerTime = `${number | ""}${number}:${number}${number}`;
const t: MarkerTime = "09:00";

to create the MarkerTime type which is type that matches a string with 1 to 2 numbers before the colon and 2 numbers after.

Therefore, we can create a MarkTime variable t with value "09:00" and the TypeScript compiler will accept it.

Conclusion

To define a regex-matched string type in TypeScript, we can create a literal type that matches the pattern of a given string.