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TypeScriptでthisの型を指定する方法

さっそく結論ですが TypeScript のバージョン 2.3 から ThisType という組み込みの型が使えるためこれを利用します。

const obj: ThisType<{ name: string }> = {
  test() {
    return this.name; // 推論できる
  }
};

日常的にはあまり使われないかもしれませんが、ライブラリの型定義などであると便利な型です。

例えば Vue.js で TypeScript を用いる際、this の型が推論されるのはライブラリ内部で ThisType を用いて型定義が行われているおかげです。

ThisType が使われている箇所:vue/options.d.ts at 731e4d0ebc997a6c2b1fc500b08924ff7ba091b6 · vuejs/vue

参考

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