typescript existence check

existence.md

Existence in Javascript (but written in Typescript)

A simple series of utility to check value existence.

function itExists(it: unknown): boolean {
  if (!hasValue(it)) return false;
  else if (Array.isArray(it)) return isArrNotEmpty(it);
  else if (typeof it === 'object') return isObjNotEmpty(it!);
  else return true;
}

function hasValue<T>(
  el: T | null | undefined
): el is Exclude<T, null | undefined | ''> {
  return el !== undefined && el !== null && el !== '';
}

function isArrNotEmpty<T>(arr: Array<T | T[] | undefined>): boolean {
  return flatten(arr).some(hasValue);
}

function isObjNotEmpty(obj: object): boolean {
  return Object.keys(obj).length > 0;
}

function flatten<T>(arr: Array<T | T[] | undefined>): (T | undefined)[] {
  return arr.reduce(
    (acc, val) =>
      Array.isArray(val) ? acc.concat(flatten(val)) : acc.concat(val),
    [] as (T | undefined)[]
  );
}

Usage

const testVar1 = '';
const testArr1 = [null, '', [null, [null]]];
const testArr2 = [null, '', '', undefined, [null, [null]]];
const testObj1 = {};
const testObj2 = {a: null};

console.log(itExists(testVar1));