js中定义enum

我们知道Js是弱类型语言，默认也无法定义枚举。我们可以通过自定义的方式实现，基础类如下:

class Enumify {
  static closeEnum () {
    const enumKeys = []
    const enumValues = []
    // Traverse the enum entries
    for (const [key, value] of Object.entries(this)) {
      enumKeys.push(key)
      value.enumKey = key
      value.enumOrdinal = enumValues.length
      enumValues.push(value)
    }
    // Important: only add more static properties *after* processing the enum entries
    this.enumKeys = enumKeys
    this.enumValues = enumValues
    // TODO: prevent instantiation now. Freeze `this`?
  }

  /** Use case: parsing enum values */
  static enumValueOf (str) {
    const index = this.enumKeys.indexOf(str)
    if (index >= 0) {
      return this.enumValues[index]
    }
    return undefined
  }

  static [Symbol.iterator] () {
    return this.enumValues[Symbol.iterator]()
  }

  toString () {
    return this.constructor.name + '.' + this.enumKey
  }
}

比如我们要定义一个Gender枚举，定义如下:

export class Gender extends Enumify {
    static MALE = new Gender(1, '男');
    static FEMALE = new Gender(2, '女');
    static _ = this.closeEnum();
    static getGenderDescribe = (value) => {
      if (value === Gender.MALE.getValue()) {
        return Gender.MALE.getDescribe()
      } else if (value === Gender.FEMALE.getValue()) {
        return Gender.FEMALE.getDescribe()
      }
      return '未知'
    }
    constructor (value, describe = '') {
      super()
      this.value = value
      this.describe = describe
    }

    getValue () {
      return this.value
    }

    getDescribe () {
      return this.describe
    }
}