JavaScript对象不会发生突变

Question

我想将对象的属性：lists_to_download: { 10920: "10920" }转换为lists_to_download: ["10920"]，所以我创建了一个处理器类，可以处理这种类型的操作，但不会使输入对象发生变化。我不知道问题出在哪里。看一下下面的代码，然后查看console.log的输出。

class ObjectKeysToArraySettingsProcessor {

  constructor(objectPath = []) {
    this.objectPath = objectPath
  }

  _preProcessRecursion(part, objectPathIndex) {
    if(_isArray(part) && objectPathIndex < this.objectPath.length - 1) {
      part.forEach(item => {
        this._preProcessRecursion(item, objectPathIndex + 1)
      })
    } else if(objectPathIndex === this.objectPath.length - 1) {
      if(_isEmpty(part)) {
        part = []
      } else {
        console.log(part) // it prints { 10920: "10920" }
        part = _map(part, id => id)
        console.log(part) // it prints ["10920"]
      }
    } else {
      this._preProcessRecursion(
        part[this.objectPath[objectPathIndex + 1]],
        objectPathIndex + 1
      )
    }
  }

  preProcessSettings(settings) {
    if(!_isEmpty(this.objectPath)) {
      try {
        this._preProcessRecursion(
          settings[this.objectPath[0]],
          0
        )
      } catch(err) {
        console.log(err)
        return settings
      }
    }
    console.log(settings) // but here it prints lists_to_downloads: { 10920: "10920" } again...
    return settings
  }
}

Answer 1

解决方案是在递归的上一步/不是最后一步进行转换

_preProcessRecursion(part, objectPathIndex) {
    if(_isArray(part) && objectPathIndex < this.objectPath.length - 1) {
      part.forEach(item => {
        this._preProcessRecursion(item, objectPathIndex + 1)
      })
    } else if(objectPathIndex === this.objectPath.length - 2) {
      const attribute = this.objectPath[objectPathIndex + 1]
      if(_isEmpty(part[attribute])) {
        part[attribute] = []
        return
      } else {
        part[attribute] = _map(
          part[attribute], id => id
        )
      }
    } else {
      this._preProcessRecursion(
        part[this.objectPath[objectPathIndex + 1]],
        objectPathIndex + 1
      )
    }
  }