Array.prototype.map() expects a value to be returned, but can’t return null as per other questions, at the end of arrow function

I am using the map function with an if statement that doesn’t end in else. I have to be strict that only the defined recourseTypes are shown.

in eslint I get an error on my => as it doesn’t end in an else

Array.prototype.map() expects a value to be returned at the end of arrow function.

Is there a correct way to write this?

Code:

   routes: async () => {
      const apiURL = process.env.BASE_URL
      const response = await axios.get(`${apiURL}/urls`)
      const { data: resources } = response.data
      const urlModule = resources.map((resource) => {
        const { resourceType } = resource

    if (resourceType === 'brand') {
      return {
        url: `/${resource.url}`,
        changefreq: 'weekly',
        priority: 0.9,
      }
    } else if (resourceType === 'product') {
      return {
        url: `/${resource.url}`,
        changefreq: 'monthly',
        priority: 0.8,
      }
    } else if (resourceType === 'category') {
      return {
        url: `/${resource.url}`,
        changefreq: 'weekly',
        priority: 0.7,
      }
    } else if (resourceType === 'document') {
      return {
        url: `/${resource.url}`,
        changefreq: 'weekly',
        priority: 0.6,
      }
    }
  })

  return [
    {
      url: '/',
      changefreq: 'daily',
      priority: 1,
    },
    {
      url: '/account',
      changefreq: 'daily',
      priority: 1,
    },
    {
      url: '/account/order-history',
      changefreq: 'daily',
      priority: 1,
    },
    ...urlModule,
  ]
},

Answer

Clarification : resources array contains all the resourceType that we are comparing using if/else clause ? As Array.map() will return the same number of elements as input array contains otherwise it will return with undefined.

Suggestion : Instead of multiple if/else-if clause, we can use multiple if statements for a better performance.

Demo :

// Response coming from API.
const resources = [{
  resourceType: 'brand',
  url: 'brandUrl'
}, {
  resourceType: 'product',
  url: 'productUrl'
}, {
  resourceType: 'category',
  url: 'categoryUrl'
}, {
  resourceType: 'document',
  url: 'documentUrl'
}];

// Array of required ResourceTypes. 
const requiredResourceTypes = ['brand', 'product', 'document'];

// Logic to filter and get the URL's object of the required resourceTypes.
const urlModule = resources.filter(({resourceType}) => requiredResourceTypes.includes(resourceType)).map((resource) => {
    const { resourceType } = resource
    if (resourceType === 'brand') {
      return {
        url: `/${resource.url}`,
        changefreq: 'weekly',
        priority: 0.9,
      }
    }
    if (resourceType === 'product') {
      return {
        url: `/${resource.url}`,
        changefreq: 'monthly',
        priority: 0.8,
      }
    }
    if (resourceType === 'category') {
      return {
        url: `/${resource.url}`,
        changefreq: 'weekly',
        priority: 0.7,
      }
    }
    if (resourceType === 'document') {
      return {
        url: `/${resource.url}`,
        changefreq: 'weekly',
        priority: 0.6,
      }
    }
  });
  
  console.log(urlModule);

Performance test result screenshot :