@novo-learning/novo-sdk/src/util/merge-deep.ts

SDK for the Novolanguage Speech Analysis API

export const isObject = <T>(item: T): item is NonNullable<T> => {
  return item != null && typeof item === 'object' && !Array.isArray(item);
};

const forbiddenProperties: string[] = ['__proto__', 'constructor', 'prototype'];

/**
 * Merges partial objects into the target object.
 * This modifies the target object and returns it.
 *
 * @param target   The object into which the changes are merged
 * @param sources  A list of patches to apply
 * @returns  the target
 */
export const mergeDeep = <T>(target: T, ...sources: Partial<T>[]): T => {
  if (!sources.length) {
    return target;
  }
  const source = sources.shift();

  if (isObject(target) && isObject(source)) {
    for (const key in source) {
      // Prevent prototype pollution
      if (!source.hasOwnProperty(key) || forbiddenProperties.includes(key)) {
        continue;
      }
      const value = source[key];

      if (isObject(value)) {
        if (!target[key]) {
          Object.assign(target, {
            [key]: {},
          });
        }
        mergeDeep(target[key], value);
      } else {
        Object.assign(target, {
          [key]: source[key],
        });
      }
    }
  }

  return mergeDeep<T>(target, ...sources);
};