我通过编辑tsconfig解决了这个问题。json文件。

下面:"strict": true， 加上这两行:

"noImplicitAny": false,
"strictNullChecks": false,

你可以像下面这样实现一个用户定义的类型:

type Nullable<T> = T | undefined | null;

var foo: Nullable<number> = 10; // ok
var bar: Nullable<number> = true; // type 'true' is not assignable to type 'Nullable<number>'
var baz: Nullable<number> = null; // ok

var arr1: Nullable<Array<number>> = [1,2]; // ok
var obj: Nullable<Object> = {}; // ok

 // Type 'number[]' is not assignable to type 'string[]'. 
 // Type 'number' is not assignable to type 'string'
var arr2: Nullable<Array<string>> = [1,2];

就加个问号?到可选字段。

interface Employee{
   id: number;
   name: string;
   salary?: number;
}

type MyProps = {
  workoutType: string | null;
};

type WithNullableFields<T, Fields> = {
  [K in keyof T]: K extends Fields 
    ? T[K] | null | undefined
    : T[K]
}

let employeeWithNullableSalary: WithNullableFields<Employee, "salary"> = {
  id: 1,
  name: "John",
  salary: null
}

或者你可以关闭strictNullChecks;)

反过来说:

type WithNonNullableFields<T, Fields> = {
  [K in keyof T]: K extends Fields
    ? NonNullable<T[K]>
    : T[K]
}

在我看来，联合类型在这种情况下是最好的选择:

interface Employee{
   id: number;
   name: string;
   salary: number | null;
}

// Both cases are valid
let employe1: Employee = { id: 1, name: 'John', salary: 100 };
let employe2: Employee = { id: 1, name: 'John', salary: null };

编辑:为了使其按预期工作，您应该在tsconfig中启用strictNullChecks。