Question

考虑以下数组的JSON表示：

logMessages = [
   {
      "timestamp":1499776056977,
      "message":"Log message c7a09226",
      "ingestionTime":1499776058327
   },
   {
      "timestamp":1499777056977,
      "message":"Log message e5d5b51a3ae1",
      "ingestionTime":1499777058327
   },
   {
      "timestamp":1499778056977,
      "message":"Log message b79f4620935b",
      "ingestionTime":1499778058327
   }
]

假设我只想保留timestamp和message并省略ingestionTime。在Python中，我会这样做：

>>> [ {'timestamp': o['timestamp'], 'message': o['message']} for o in logMessages]

[{'timestamp': 1499776056977, 'message': 'Log message c7a09226'},
 {'timestamp': 1499777056977, 'message': 'Log message e5d5b51a3ae1'}, 
 {'timestamp': 1499778056977, 'message': 'Log message b79f4620935b'}]

如何在Javascript中进行相同的字段过滤？

Answer 1

您可以使用对象解构来获取密钥的子集。

> logMessages= [ 
  { timestamp: 1499776056977,
    message: 'Log message c7a09226',
    ingestionTime: 1499776058327 },
  { timestamp: 1499777056977,
    message: 'Log message e5d5b51a3ae1',
    ingestionTime: 1499777058327 },
  { timestamp: 1499778056977,
    message: 'Log message b79f4620935b',
    ingestionTime: 1499778058327 } ]

> logMessages.map(({ timestamp, message }) => ({ timestamp, message }));

[ { timestamp: 1499776056977, message: 'Log message c7a09226' },
  { timestamp: 1499777056977,
    message: 'Log message e5d5b51a3ae1' },
  { timestamp: 1499778056977,
    message: 'Log message b79f4620935b' } ]

可以找到解构分配语法的文档：

Mozilla Develoepr Network

Answer 2

.map with an arrow function does诀窍：

logMessages= [ 
  { timestamp: 1499776056977,
    message: 'Log message c7a09226',
    ingestionTime: 1499776058327 },
  { timestamp: 1499777056977,
    message: 'Log message e5d5b51a3ae1',
    ingestionTime: 1499777058327 },
  { timestamp: 1499778056977,
    message: 'Log message b79f4620935b',
    ingestionTime: 1499778058327 } ]

> logMessages.map( (o) => {return {timestamp: o.timestamp, message: o.message}})
[ { timestamp: 1499776056977, message: 'Log message c7a09226' },
  { timestamp: 1499777056977,
    message: 'Log message e5d5b51a3ae1' },
  { timestamp: 1499778056977,
    message: 'Log message b79f4620935b' } ]

在Javascript中相当于Python的列表理解

2 个答案: