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How to create a new object from a specified object where all keys are lowercase in JavaScript?

WBOYforward: 2023-09-17 12:09:06484browse

如何从指定对象创建一个新对象，其中所有键在 JavaScript 中都是小写？

In JavaScript, there are many ways to create new objects from old objects. Creating a new object with the same keys as an existing object but with all keys in lowercase is a common use case. This is helpful when working with data from many sources with irregular key casing. In this blog post, we will look at various JavaScript methods for creating new objects using lowercase keys.

Before we do that, however, it's important to remember that while creating new objects with lowercase keys can be helpful when working with data from a variety of sources, it's also important to be aware of the possible consequences of changing key case.

For example, it might break code that currently expects a key to be in a certain situation, or it might interfere with an external API or database that expects a key to be in a certain situation. Before changing the key case of an object, always run thorough tests on your code and consider the specific requirements of your use case.

Object.assign()

New objects can be created by joining one or more existing objects together using the built-in JavaScript method Object.assign(). It is also possible to change an object's key shell by generating a new object with the same keys as the original object but with all keys in lowercase. Basic syntax for creating a new object with lowercase keys using Object.assign().

Example

<html>
<body>
   <div id="myDiv"></div>
   <script>
      var original = {name: "John", AGE: 25};
      var lowercase = Object.assign({}, original);
      document.getElementById("myDiv").innerHTML = JSON.stringify(lowercase);
   </script>
</body>
</html>

In this example, the function Object.assign() generates a new object and assigns it the properties of the original object. The same keys from the old object will appear in the new object, but they will be lowercase.

You can use the Object.keys() function to iterate over the keys of the original object and change them to lowercase before passing them to Object.assign() -

Example

<html>
<body>
   <div id="myDiv"></div>
   <script>
      var original = { name: "John", AGE: 25 };
      var lowercase = Object.assign(
         {},
         ...Object.keys(original).map((k) => ({
            [k.toLowerCase()]: original[k],
         }))
      );
      document.getElementById("myDiv").innerHTML = JSON.stringify(lowercase);
   </script>
</body>
</html>

This method uses the Object.keys() method to get the keys array of the original object. The Array.map() method is used to iterate over the keys and create a new object with the same keys but in lowercase. The new object is then passed to Object.assign() using the spread operator.

for-in loop

Using a for-in loop to iterate over the keys of the original object and generate a new object with the same keys but in lowercase is another way to build a new object with lowercase keys. The basic syntax for using a for-in loop to create a new object with lowercase keys is -

Example

<html>
<body>
   <div id="myDiv"></div>
   <script>
      var original = { name: "John", AGE: 25 };
      var lowercase = {};
      for (var key in original) {
         lowercase[key.toLowerCase()] = original[key];
      }
      document.getElementById("myDiv").innerHTML = JSON.stringify(lowercase);
   </script>
</body>
</html>

In this example, the toLowerCase() function is used to change each key from uppercase to lowercase and assign the associated value to the new object. Then the for-in loop iterates over the keys of the original object.

JSON.parse() and JSON.stringify()

Using the JSON.parse() and JSON.stringify() methods is a third way to create new objects with lowercase keys. When using these techniques to construct new objects with lowercase keys, the basic syntax is -

Example

<html>
<body>
   <div id="myDiv"></div>
   <script>
      var original = { name: "John", AGE: 25 };
      var lowercase = JSON.parse(JSON.stringify(original).toLowerCase());
      document.getElementById("myDiv").innerHTML = JSON.stringify(lowercase);
   </script>
</body>
</html>

In this example, use the JSON.stringify() method to convert the original object to a JSON string. Then use the toLowerCase() method to convert all keys in the JSON string to lowercase.

Finally, use the JSON.parse() method to convert the JSON string back into a JavaScript object. By using this method, a new object is created that has the same keys as the original object, but with all keys in lowercase.

In fact, this method requires converting the object to a string and back again, which makes it less efficient than the first two methods. It also only works with simple objects; it may not work with objects with unique properties or methods.

in conclusion

In this article, we looked at various JavaScript methods for constructing new objects with lowercase keys. A quick and efficient way to generate a new object with the same keys as an existing object but all lowercase is to use the Object.assign() method. Another option to iterate over the keys of an object and generate a new object with the same keys but in lowercase is a for-in loop. Lowercase keys can also be used to construct new objects using the JSON.parse() and JSON.stringify() methods, although this method is less efficient and may not work with all types of objects.

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How to create a new object from a specified object where all keys are lowercase in JavaScript?

Object.assign()

Example

Example

for-in loop

Example

JSON.parse() and JSON.stringify()

Example

in conclusion

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