# E0225: index signatures require a value type

A TypeScript index signature has a key type and a value type. It is a syntax error to omit the value type:

    interface StringArray {
      readonly [index: number];
    }

    interface StringDictionary {
      [k: string];
    }

To fix this error, write `:` then the type of the value:

    interface StringArray {
      readonly [index: number]: string;
    }

    interface StringDictionary {
      [k: string]: any;
    }

Introduced in quick-lint-js version 2.6.0.

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