msw/src/core/utils/internal/mergeRight.ts

Seamless REST/GraphQL API mocking library for browser and Node.js.

import { isObject } from './isObject'

/**
 * Deeply merges two given objects with the right one
 * having a priority during property assignment.
 */
export function mergeRight(
  left: Record<string, any>,
  right: Record<string, any>,
) {
  return Object.entries(right).reduce(
    (result, [key, rightValue]) => {
      const leftValue = result[key]

      if (Array.isArray(leftValue) && Array.isArray(rightValue)) {
        result[key] = leftValue.concat(rightValue)
        return result
      }

      if (isObject(leftValue) && isObject(rightValue)) {
        result[key] = mergeRight(leftValue, rightValue)
        return result
      }

      result[key] = rightValue
      return result
    },
    Object.assign({}, left),
  )
}