Aquí está el código con error:
let createArray = function<T>(length: number, value: T): T[] { let result: T[] = []; for (let i = 0; i < length; i++) { if (typeof value === 'string') { result[i] = value + '_' + i; // Type 'string' is not assignable to type 'T'. 'T' could be instantiated with an arbitrary type which could be unrelated to 'string'. } else { result[i] = value; } } return result; } createArray(3, 'x'); No tengo idea de por qué Typescript no puede reconocer Generics T como string en este caso.
¿Cómo puedo arreglarlo?
Usar sobrecarga :
function createArray(length: number, value: string): string[]; function createArray<T>(length: number, value: T): T[]; function createArray<T>(length: number, value: T|string): (T|string)[] { let result = []; for (let i = 0; i < length; i++) { if (typeof value === 'string') { result[i] = value + '_' + i; // Type 'string' is not assignable to type 'T'. 'T' could be instantiated with an arbitrary type which could be unrelated to 'string'. } else { result[i] = value; } } return result; } console.log(createArray(3, 'x')); // ["x_0", "x_1", "x_2"] console.log(createArray(3, 23)); // [23, 23, 23] console.log(createArray(3, {hi: "hello"})); // [{ // "hi": "hello" // }, { // "hi": "hello" // }, { // "hi": "hello" // }]Ver demostración .