Deep Merge and Shallow Merge

merge-objects.ts

export const shallowMerge = <T extends object = Record<string, any>>(
  ...objects: T[]
): T => {
  return objects.reduce((prev, cur) => ({ ...prev, ...cur }), {} as T);
};

export const deepMerge = <T extends object = Record<string, any>>(
  target: T,
  ...sources: object[]
): T => {
  const merge = (target: object, source: object) => {
    Object.keys(source).forEach((key: string) => {
      const targetValue = target[key];
      const sourceValue = source[key];
      if (Array.isArray(targetValue) && Array.isArray(sourceValue)) {
        target[key] = targetValue.concat(sourceValue);
      } else if (is.object(targetValue) && is.object(sourceValue)) {
        target[key] = merge(Object.assign({}, targetValue), sourceValue);
      } else {
        target[key] = sourceValue;
      }
    });
    return target;
  };
  return sources.reduce((prev, cur) => merge(prev, cur), target) as T;
};