Category: TypeScript

Sometimes, we want to fix Typescript error "This condition will always return ‘true’ since the types have no overlap".

In this article, we’ll look at how to fix Typescript error "This condition will always return ‘true’ since the types have no overlap".

How to fix Typescript error "This condition will always return ‘true’ since the types have no overlap"?

To fix Typescript error "This condition will always return ‘true’ since the types have no overlap", we should make sure our boolean isn’t always true.

For instance, we write

const frType: "Child" | "Infant" = "Child";
const rightType = frType !== "Child" || frType !== "Infant";

then we get the error because frType can either be 'Child' or 'Infant'.

But we’re checking if frType isn’t 'Child' or 'Infant', which means it always returns true since frType can only be 1 of the 2 values.

Conclusion

To fix Typescript error "This condition will always return ‘true’ since the types have no overlap", we should make sure our boolean isn’t always true.

Sometimes, we want to add environment variables with dotenv and TypeScript.

In this article, we’ll look at how to add environment variables with dotenv and TypeScript.

How to add environment variables with dotenv and TypeScript?

To add environment variables with dotenv and TypeScript, we call the dotenv.config method.

For instance, we write

import * as dotenv from "dotenv";
dotenv.config({ path: __dirname + "/.env" });

to call dotenv.config with an object with the path of the environment variable file to load the key-value pairs into process.env.

Conclusion

To add environment variables with dotenv and TypeScript, we call the dotenv.config method.

Sometimes, we want to disable all TypeScript type checking.

In this article, we’ll look at how to disable all TypeScript type checking.

How to disable all TypeScript type checking?

To disable all TypeScript type checking, we set the checkJs option to false.

For instance, we write

{
  "compilerOptions": {
    //...
    "checkJs": false
    //...
  }
}

in tsconfig.json to disable all type checks by setting checkJs to false in compilerOptions.

Conclusion

To disable all TypeScript type checking, we set the checkJs option to false.

Sometimes, we want to fix Element implicitly has an ‘any’ type because expression of type ‘string’ can’t be used to index type with TypeScript.

In this article, we’ll look at how to fix Element implicitly has an ‘any’ type because expression of type ‘string’ can’t be used to index type with TypeScript.

How to fix Element implicitly has an ‘any’ type because expression of type ‘string’ can’t be used to index type with TypeScript?

To fix Element implicitly has an ‘any’ type because expression of type ‘string’ can’t be used to index type with TypeScript, we use index signatures.

For instance, we write

const color: { [key: string]: any } = {
  red: null,
  green: null,
  blue: null,
};

to add the { [key: string]: any } type to color.

[key: string] is the index signature and it lets us add any string key into the object with the type.

The property value can be anything.

Conclusion

To fix Element implicitly has an ‘any’ type because expression of type ‘string’ can’t be used to index type with TypeScript, we use index signatures.

To fix Uncaught ReferenceError: exports is not defined in filed generated by TypeScript, we fix the project config.

In tsconfig.json, we write

{
  "compilerOptions": {
    "target": "ESNext",
    "module": "CommonJS",
    "lib": ["DOM", "ES5"],
    "esModuleInterop": true
  }
}

to set esModuleInterop to true to compile ES6 modules.

And we remove "type": "module" from package.json to fix the error.