Type 'number' is not assignable to type 'never'. using fill array?

Question

interface Itype { 
    type: number;
    name?: string;
}

function makeEqualArrays(arr1: Itype[], arr2: Itype[]): void { 
      arr2 = arr2.concat([].fill({ type: 2 }, len1 - len2));
}

Why I can not fill array by object?

Type 'number' is not assignable to type 'never'.

Orelsanpls · Answer

You have to type the new array you are creating [] like :
([] as Itype[])

playground
interface Itype { 
    type: number;
    name?: string;
}

function makeEqualArrays(arr1: Itype[], arr2: Itype[]): void { 
    arr2 = arr2.concat(([] as Itype[]).fill({
        type: 2,name
    }, 5));
}

One Answer