Question

我使用Express并拥有一组对象。我想修改created属性（我正在使用dateFormat包）进行演示。

该数组是mongo查询的结果，并分配给变量stories，如下所示：

[
    { public: false,
      keyStageLevel: [ 'ks1' ],
      created: 2018-03-25T13:01:30.809Z,
      _id: 5ab79daafa832035b416536f,
      slug: 'goldilocks',
      name: 'Goldilocks',
      comments: null,
      id: '5ab79daafa832035b416536f' },
    { public: false,
      keyStageLevel: [ 'ks1' ],
     created: 2018-03-25T13:07:22.421Z,
     _id: 5ab79f0afa832035b4165370,
     slug: 'cinderella',
     name: 'Cinderella',    
     comments: null,
     id: '5ab79f0afa832035b4165370' },
   ..
]

如果我执行

stories.map(function(story){
    story.created = dateFormat(story.created, "dddd, mmmm dS, yyyy, h:MM:ss TT")
    console.log('AFTER TRANSFORM '+story.created);
});

console.log显示了我想要的日期格式，但story.created数组中的stories值未经修改。什么是正确的方法（ES5，如果可能，我学习并且我发现更容易理解发生了什么）重新格式化created数组中的stories属性？

修改 - 显示.map和.foreach的查询和使用，两者都会留下“故事”。未修饰的

let stories = await Story.find({$or:[{'group': {$in:group}}, 
  {'public':true} ]})
    .populate('group')
    .populate('createdBy');
console.log('BEFORE TRANSFORM '+stories);
// console.log(stories);
// stories.map(function(story){
//     story.created = dateFormat(story.created, "dddd, mmmm dS, yyyy, h:MM:ss TT")
//     console.log('AFTER TRANSFORM '+story.created);
// });
stories.forEach(story => {
    story.created = dateFormat(story.created, "dddd, mmmm dS, yyyy, h:MM:ss TT")
});
console.log('AFTER TRANSFORM '+stories);

Answer 1

正如其他人所说，您误导map。不过，我的选择是正确使用map，并从旧版本中创建一个新数组。我认为对未发生变异的数据进行推理要容易得多。这是一种方法：

＆＃13;

const stories = [{"_id": "5ab79daafa832035b416536f", "comments": null, "created": "2018-03-25T13:01:30.809Z", "id": "5ab79daafa832035b416536f", "keyStageLevel": ["ks1"], "name": "Goldilocks", "public": false, "slug": "goldilocks"}, {"_id": "5ab79f0afa832035b4165370", "comments": null, "created": "2018-03-25T13:07:22.421Z", "id": "5ab79f0afa832035b4165370", "keyStageLevel": ["ks1"], "name": "Cinderella", "public": false, "slug": "cinderella"}]

const dateFormat = (d) => d.slice(0, 10) // dummy

const updatedStories = 
    stories.map(story => ({...story, created: dateFormat(story.created)}))

console.log(updatedStories)

＆＃13;

如果ES6困扰你，那么你可以用

替换它

stories.map(story => Object.assign({}, story, {created: dateFormat(story.created)}))

Answer 2

您可能需要考虑forEach()：

stories.forEach(story => {
    story.created = dateFormat(story.created, "dddd, mmmm dS, yyyy, h:MM:ss TT")
});

文档： Array.prototype.forEach() - JavaScript | MDN

修改JavaScript数组属性

2 个答案: