some javascript helper methods i've used in various projects

javascriptHelpers.js

export const nestArray = (items, parent = '#') => {
    const nested = [];
    Object.values(items).forEach(item => {
        if (item.parent == parent) {
            const fetchedChildren = nestArray(items, item.id);

            if (fetchedChildren.length) {
                item.fetchedChildren = fetchedChildren;
            }
            nested.push(item);
        }
    });
    return nested;
};

export const flattenArray = (items) => {
    var result = [];
    for (let item of items) {
        if (item) {
            result.push(item)
            if (item.fetchedChildren) {
                result = result.concat(flattenArray(item.fetchedChildren));
            }
        }
    }
    return result;
}

export function deepCopy(obj) {
    if(typeof obj !== 'object' || obj === null) {
        return obj;
    }

    if(obj instanceof Date) {
        return new Date(obj.getTime());
    }

    if(obj instanceof Array) {
        return obj.reduce((arr, item, i) => {
            arr[i] = deepCopy(item);
            return arr;
        }, []);
    }

    if(obj instanceof Object) {
        return Object.keys(obj).reduce((newObj, key) => {
            newObj[key] = deepCopy(obj[key]);
            return newObj;
        }, {})
    }
}

export function getContrastYIQ(hexcolor) {
  const replacedColor = hexcolor.replace('#', '');
  const r = parseInt(replacedColor.substr(0, 2), 16);
  const g = parseInt(replacedColor.substr(2, 2), 16);
  const b = parseInt(replacedColor.substr(4, 2), 16);
  const yiq = (r * 299 + g * 587 + b * 114) / 1000;
  return yiq >= 128 ? 'black' : 'white';
}

export function multiplesOf(numbers, number) {
  var multiples = [];
  for (var i = 0; i < numbers.length; i++) {
    if (numbers[i] % number === 0) {
      multiples.push(numbers[i]);
    }
  }

  return multiples;
}

export function convertNumber(number, format) {
  let tail = format.lastIndexOf('.');
  let convertedNumber = number.toString();
  let formatter = format;
  tail = tail > -1 ? format.substr(tail) : '';
  if (tail.length > 0) {
    if (tail.charAt(1) === '#') {
      tail = convertedNumber.substr(convertedNumber.lastIndexOf('.'), tail.length);
    }
  }
  convertedNumber = convertedNumber.replace(/\..*|[^0-9]/g, '').split('');
  formatter = formatter.replace(/\..*/g, '').split('');
  for (let i = format.length - 1; i > -1; i += 1) {
    if (format[i] === '#') {
      formatter[i] = convertedNumber.pop();
    }
  }
  return convertedNumber.join('') + formatter.join('') + tail;
}

function getListOfValues() {
  return new Array(20).fill().map((_, i) => ({ label: i, value: i }));
}