set-or-delete.js

const cloneDeep = require("lodash/cloneDeep")

function sameKeys(dstKeys, srcKeys) {
  // keys are from an array so they are in order
  if (dstKeys.length !== srcKeys.length) return false
  for (let i = 0; i < dstKeys.length; i++) {
    if (dstKeys[i] !== srcKeys[i]) {
      return false
    }
  }
  return true
}

function stringify(obj, key) {
  const value = obj[key]
  if (typeof value === "undefined" && !Object.keys(obj).includes(key))
    return "not-present"
  if (typeof value === "function") return (value.name || "unnamed") + "()"
  return JSON.stringify(value, null, 2)
}

function setOrDeleteKeyWithMessages(dst, src, messages, keyPath, key) {
  if (
    typeof dst[key] === "object" &&
    typeof src[key] === "object" &&
    dst[key] !== null &&
    src[key] !== null
  )
    setOrDeleteWithMessages(dst[key], src[key], messages, keyPath)
  else {
    if (typeof src[key] === "object" && src[key] !== null) {
      if (messages)
        messages.push(
          `${keyPath}: changing ${stringify(dst, key)} to ${stringify(
            src,
            key
          )}`
        )
      dst[key] = cloneDeep(src[key])
    } else if (dst[key] !== src[key]) {
      if (messages)
        messages.push(
          `${keyPath}: changing ${stringify(dst, key)} to ${stringify(
            src,
            key
          )}`
        )
      dst[key] = src[key]
    }
  }
}

export default function setOrDeleteWithMessages(dst, src, messages, keyPath) {
  if (
    typeof dst === "object" &&
    typeof src === "object" &&
    dst !== null &&
    src !== null
  ) {
    const dstKeys = Object.keys(dst)
    const srcKeys = Object.keys(src)
    if (Array.isArray(dst) && Array.isArray(src)) {
      for (const key of srcKeys)
        setOrDeleteKeyWithMessages(
          dst,
          src,
          messages,
          `${keyPath ? keyPath : ""}[${key}]`,
          key
        )
      if (!sameKeys(dstKeys, srcKeys)) {
        for (const key of dstKeys.reverse()) {
          // reverse because splice changes order each time
          if (srcKeys.includes(key)) continue
          else {
            if (messages)
              messages.push(
                `deleting ${keyPath ? keyPath : ""}[${key}]: ${dst[key]}`
              )
            dst.splice(key, 1)
          }
        }
        return
      }
    } else {
      for (const key of srcKeys) {
        if (typeof src[key] === "undefined") {
          if (messages)
            messages.push(
              `deleting ${keyPath ? keyPath + "." : ""}${key}: ${dst[key]}`
            )
          delete dst[key]
        } else
          setOrDeleteKeyWithMessages(
            dst,
            src,
            messages,
            (keyPath ? keyPath + "." : "") + key,
            key
          )
      }
    }
  } else {
    if (messages)
      messages.push(
        `${
          keyPath ? keyPath + ": c" : "C"
        }an not change type ${typeof dst} to ${typeof src}`
      )
  }
}