javascript - 更改对象的嵌套属性

Question

型号:

function model() {
    return {
        title: { 
            "content": undefined,
            "validation": {
                "type": "string",
                "required": true,
                "minLength": 1,
                "maxLength": 3,
                validationErrorMessage: "Your title must be a valid string between 1 and 35 characters"
            }
        },

        email: {
            content: undefined,
            validation: {
                type: "email",
                required: true,
                minLength: 1,
                maxLength: 60,
                validationErrorMessage: "Your email must be between 1 and 50 characters"
            }
        },


        link: {
            content: undefined,
            validation: {
                type: "url",
                required: true,
                minLength: 1,
                maxLength: 500,
                validationErrorMessage: "Your link name must be a valid email between 1 and 50 characters"
            }
        },

        description: {
            content: undefined
        }
    }
}

lambda 代码:

 let test = R.map( x => console.log(x.validation), model)
 console.log(test)

记录正确的结果:

{ type: 'string',
  required: true,
  minLength: 1,
  maxLength: 3,
  validationErrorMessage: 'Your title must be a valid string between 1 and 35 characters' }
{ type: 'email',
  required: true,
  minLength: 1,
  maxLength: 60,
  validationErrorMessage: 'Your email must be between 1 and 50 characters' }
{ type: 'url',
  required: true,
  minLength: 1,
  maxLength: 500,
  validationErrorMessage: 'Your link name must be a valid email between 1 and 50 characters' }
undefined
{ title: undefined,
  email: undefined,
  link: undefined,
  description: undefined }

那为什么会这样:

   let test = R.map( x => x.validation = "replacement test", model)
   console.log(test)

日志:

{ title: 'replacement test',
  email: 'replacement test',
  link: 'replacement test',
  description: 'replacement test' }

我本以为 x.validation 内容会被替换，而不是整个 x 值。我不明白。

Answer 1

map，就像所有 Ramda 函数一样，旨在以不可变的方式使用。它返回一个列表，其中包含您从函数返回的元素。但是你不会(有意地)从你的函数中返回任何东西，只是调整原始值。不过，Javascript 正在从您的赋值表达式中返回，这是 ES6 箭头函数的一个很好的特性。

如果你想保持你的对象完好无损，但更新'validation'属性，这可能会做:

R.map(R.assoc('validation', 'replacement text'), model());

assoc对您的对象进行浅表克隆，用给定的值覆盖指定的属性。