Product stock with Snipcart Javascript API

snipcart.js

const API_KEY = 'XXXXXXXXXXXXXXXXX'

export const fetchStock = async (productId = '') => {
  try {
    const response = await fetch(`https://app.snipcart.com/api/products/${productId}`, {
      headers: {
        'Authorization': 'Basic ' + Buffer.from(API_KEY + ':').toString('base64'),
        'Accept': 'application/json',
      },
    }).then(res => res.json())

    if (productId !== '') {
      const product = response
      
      if (product.userDefinedId) {
        return {
          id: product.userDefinedId,
          stock: product.allowOutOfStockPurchases ? true : product.stock,
        }
      } else {
        return {
          error: true,
          message: `No product with id: "${productId}" found.`
        }
      }
    } else {
      if (response.items) {
        let stockProducts = []
        const products = response.items

        if (products.length > 0) {
          stockProducts = products.map(product => {
            return {
              id: product.userDefinedId,
              stock: product.allowOutOfStockPurchases ? true : product.stock,
            }
          })
        }

        return stockProducts
      } else {
        return {
          error: true,
          message: 'No products found.'
        }
      }
    }
  } catch(err) {
    return {
      error: true,
      message: String(err)
    }
  }
}