javascript - 将 JSON 对象键转换为小写

Question

所以我有以下 JSON 对象:

var myObj = {
   Name: "Paul",
   Address: "27 Light Avenue"
}

我想将它的键转换为小写，这样我会得到:

var newObj = {
   name: "Paul",
   address: "27 Light Avenue"
}

我尝试了以下方法:

var newObj = mapLower(myObj, function(field) {
    return field.toLowerCase();
})

function mapLower(obj, mapFunc) {
    return Object.keys(obj).reduce(function(result,key) {
         result[key] = mapFunc(obj[key])
         return result;
    }, {})
}

但我收到一条错误消息，提示“未捕获的 TypeError:field.toLowerCase 不是函数”。

Answer 1

我真的不确定你想用 mapLower 函数做什么，但你似乎只传递了一个参数，即对象值。

尝试这样的事情(非递归)

var myObj = {
   Name: "Paul",
   Address: "27 Light Avenue"
}

const t1 = performance.now()

const newObj = Object.fromEntries(Object.entries(myObj).map(([ key, val ]) =>
  [ key.toLowerCase(), val ]))

const t2 = performance.now()

console.info(newObj)
console.log(`Operation took ${t2 - t1}ms`)

这将获取所有对象条目(键/值对数组)并将它们映射到一个新数组，其中键小写，然后从这些映射条目创建新对象。

---

如果您需要它来处理嵌套对象，则需要使用递归版本

var myObj = {
  Name: "Paul",
  Address: {
    Street: "27 Light Avenue"
  }
}

// Helper function for detection objects
const isObject = obj => 
  Object.prototype.toString.call(obj) === "[object Object]"

// The entry point for recursion, iterates and maps object properties
const lowerCaseObjectKeys = obj =>
  Object.fromEntries(Object.entries(obj).map(objectKeyMapper))
  
// Converts keys to lowercase, detects object values
// and sends them off for further conversion
const objectKeyMapper = ([ key, val ]) =>
  ([
    key.toLowerCase(), 
    isObject(val)
      ? lowerCaseObjectKeys(val)
      : val
  ])

const t1 = performance.now()

const newObj = lowerCaseObjectKeys(myObj)

const t2 = performance.now()

console.info(newObj)
console.log(`Operation took ${t2 - t1}ms`)