Object Key Case

Utilty package that converts all keys in an object to/from camelCase or snake_case.

Motivation

It's an unwritten rule that all keys in a JavaScript object should be camelCase. However, there are times when you need to convert to/from snake_case for use with a database or API. This package provides a simple way to convert between the two.

Installation

npm install @nolawnchairs/object-key-case

Usage

The functional approach is to use the convertKeyCase function.

import { convertKeyCase } from '@nolawnchairs/object-key-case'

// An API request returns an object with snake_case keys
const data = await fetch('https://example.com/api')
    .then((res) => res.json())
    .then((data) => convertKeyCase(data, 'camel'))

There is also the object-oriented approach using the KeyConversionContext class. This class when instantiated will retain state, which caches the conversion result for each key. This is beneficial when processing an array of multiple objects of the same shape, or many requests over time, as the regex-based conversion only needs to be computed once per key.

import { KeyConversionContext } from '@nolawnchairs/object-key-case'

// Create a context for converting to camelCase
// All key conversions will be cached within this context
const context = new KeyConversionContext('camel')

// An API request returns an object with snake_case keys
const data = await fetch('https://example.com/api')
    .then((res) => res.json())
    .then((data) => context.convert(data))

Both convertKeyCase and KeyConversionContext#convert either accept an object with key value pairs or an array of the same. An error will be thrown if any other data type is provided. For convenience, all errors thrown by this package are instances of ConversionException. This is simply a subclass of Error that can be matched in a catch block using instanceof.

import { convertKeyCase, KeyConversionException } from '@nolawnchairs/object-key-case'

try {
    convertKeyCase('not an object', 'camel')
} catch (e) {
    if (e instanceof KeyConversionException) {
        // Handle error
    }
}

The value arguments for convertKeyCase and KeyConversionContext#convert accept an unknown type, and an optional generic type T and will return T | Array<T>. The generic is applied to the result of the operation. If no type argument is provided, the return type will be unknown | Array<unknown>.

import { convertKeyCase } from '@nolawnchairs/object-key-case'

interface User {
    id: number
    firstName: string
    lastName: string
}

const data = await fetch('https://example.com/api')
    .then((res) => res.json())
    .then((data) => convertKeyCase<User>(data, 'camel'))
    // data is now of type User or Array<User>

Note that no data validation is performed. If the input data is not of the expected shape, the result will be unpredictable.