Typescript threw an error: expected 0 arguments but received one (this)

While attempting to convert some javascript code into typescript, I came across this error: https://i.sstatic.net/QTIpe.png

I'm a bit confused because it's expecting an argument

interface Command {
  execute: (client: Client, message: Message) => void;
  init: (this: this) => void;
  help: {
    name: string;
    aliases: string[];
  };
  conf: {
    location: string;
  };
}

It clearly states that it requires an argument:
https://i.sstatic.net/AH8Qa.png

Could this be related to me passing in this? I'm unsure why it's behaving like this.


Here is my tsconfig.json configuration:

{
  "compilerOptions": {
    "baseUrl": ".",
    "outDir": "build",
    "module": "esnext",
    "target": "es5",
    "lib": [
      "es6",
      "dom",
      "esnext.asynciterable"
    ],
    "sourceMap": true,
    "allowJs": true,
    "jsx": "react",
    "moduleResolution": "node",
    "rootDir": "src",
    "forceConsistentCasingInFileNames": true,
    "noImplicitReturns": true,
    "noImplicitThis": true,
    "noImplicitAny": true,
    "strictNullChecks": true,
    "suppressImplicitAnyIndexErrors": true,
    "noUnusedLocals": true,
    "skipLibCheck": true,
    "allowSyntheticDefaultImports": true
  },
  "exclude": [
    "node_modules",
    "build",
    "scripts",
    "acceptance-tests",
    "webpack",
    "jest",
    "src/setupTests.ts"
  ]
}

Answer №1

When a function is typed with what appears to be an argument called this, it actually interprets it as the context in which the function is called.

If you're expecting props to act as the this reference - essentially the Command - you can simply invoke it like this:

props.init();

By doing this, the props object will be passed as the this parameter into the function, allowing TypeScript to properly identify it.

In other scenarios where you need to pass a different context as the this reference into a function, you can use .call, for example:

props.init.call(someOtherThis);

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