打字稿：为什么number / string / ...可赋值为null？

Question

为什么TypeScript在将字符串分配给数字时只显示错误，而在为数字赋值为null时却不显示错误？

export type ArrayWithNumberOrString = Array<number | string>;
export type ArrayWithNumberOrNull = Array<number | null>;


function doSomethingWithNumbersOnly(array: number[]): number[] {
  return array;
};

const numbersAndString: ArrayWithNumberOrString = [1, 2, 3, 'string'];
const numbersAndNull: ArrayWithNumberOrNull = [1, 2, 3, null];

doSomethingWithNumbersOnly(numbersAndString);
doSomethingWithNumbersOnly(numbersAndNull);

Items

Answer 1

立即找到答案：

默认情况下，tsconfig.json中禁用了选项strictNullChecks。