Sometimes, we want to turn all the keys of an object to lower case with JavaScript.

In this article, we’ll look at how to turn all the keys of an object to lower case with JavaScript.

How to turn all the keys of an object to lower case with JavaScript?

To turn all the keys of an object to lower case with JavaScript, we can use the Object.entries and Object.fromEntries method and the string toLowerCase method.

For instance, we write

const newObj = Object.fromEntries(
  Object.entries(obj).map(([k, v]) => [k.toLowerCase(), v])
);

to call Object.fromEntries with the array returned by Object.entries and map.

Object.entries returns the key-value pairs in obj as an array of key-value pair arrays.

Therefore, we can call map on the returned array to return the lower case version of key k with k.toLowerCase.

Then we call Object.fromEntries to convert the array of key value pairs with the keys in lower case back to an object and assign it to newObj.

Conclusion

To turn all the keys of an object to lower case with JavaScript, we can use the Object.entries and Object.fromEntries method and the string toLowerCase method.