flats an array of numbers

flatten.ts

type arr = number[];
type multiple = number[][];
type irregular = any[];

const flatten = (arr : arr | multiple | irregular) : number[] => {
  const newState : number[] = [];

  for (let item of arr) {

    if (Array.isArray(item)) {
      flatten(item).forEach(val => {
        newState.push(val);
      });
    }
    else {
      newState.push(item);
    }

  }

  return newState;
};


export default flatten;