元素隐式具有'any‘类型，因为类型'any’的表达式不能用于索引类型{ 1: number；2: number；3: number；}‘

Question

以下代码抛出：

Element implicitly has an 'any' type because the expression of type 'any' can't be used to index type '{ 1: number; 2: number; 3: number; }'.

const obj = {
  1: 1,
  2: 2,
  3: 3,
}

fetch('http://example.com/foo.json')
  .then(response => response.json())
  //                         throws
  .then(data => console.log(obj[data]))

而不是列出所有可能的键：

const obj = {
  1: 1,
  2: 2,
  3: 3,
}

fetch('http://example.com/foo.json')
  .then(response => response.json())
  //                                  list all possible keys
  .then(data => console.log(obj[data as 1 | 2 | 3]))

有更好的方法来修正这个错误吗？

Answer 1

单线：

const obj = {
  1: 1,
  2: 2,
  3: 3,
}

fetch('http://example.com/foo.json')
  .then(response => response.json())
  //                                  one-liner
  .then(data => console.log(obj[data as keyof typeof obj]))