prefer-as-const.md

prefer-as-const

Prefer usage of as const over literal type.

This rule recommends usage of const assertion when type primitive value is equal to type.

Rule Details

Examples of code for this rule:

❌ Incorrect

let bar: 2 = 2;
let foo = <'bar'>'bar';
let foo = { bar: 'baz' as 'baz' };

✅ Correct

let foo = 'bar';
let foo = 'bar' as const;
let foo: 'bar' = 'bar' as const;
let bar = 'bar' as string;
let foo = <string>'bar';
let foo = { bar: 'baz' };

Options

// .eslintrc.json
{
  "rules": {
    "@typescript-eslint/prefer-as-const": "error"
  }
}

This rule is not configurable.

When Not To Use It

If you are using TypeScript < 3.4

Attributes

• ✅ Recommended
• 🔧 Fixable
• 💭 Requires type information