Can I write my own custom rule in eslint config?

Question

Is it possible to write custom rule in eslint config? My case is based on type 'any'. In eslint doc is rule "@typescript-eslint/no-explicit-any", but it's too strong for me. I want to block assignment like this:

const dontknow: any = ''; const name: string = dontknow;

Is it possible to block this case?

Answer 1

You can use the no-unsafe-assignment rule instead of the no-explicit-any rule.

This rule disallows assigning any to a variable, and assigning any[] to an array destructuring. This rule also compares the assigned type to the variable's type to ensure you don't assign an unsafe any in a generic position to a receiver that's expecting a specific type. For example, it will error if you assign Set to a variable declared as Set.

.eslintrc

  {
        "root": true,
        "parser": "@typescript-eslint/parser",
        "plugins": [
          "@typescript-eslint"
        ],
        "extends": [
          "eslint:recommended",
          "plugin:@typescript-eslint/eslint-recommended",
          "plugin:@typescript-eslint/recommended"
        ],
        "rules": { 
            "@typescript-eslint/no-unsafe-assignment": 2
        },
        "overrides": [
            {
              "files": ["*.ts", "*.tsx"], // Your TypeScript files extension
              "parserOptions": {
                "project": ["./tsconfig.json"], // Specify it only for TypeScript files
              },
            },
          ],
      }