example.ts

//1

const push = (array: number[], num: number) => {
    array[array.length] = num;
    return array
}

// 2
const pop = (array: number[]) => {
    array.length--
    return array
}

// 3 
const shift = (array: number[]): number[] => {
    const [removed, ...newArr] = array
    //array[array.length - 1] = 0
    return newArr;
  };