Identical code behaving differently. Help!

Tell us what’s happening:
While revising, I completed a challenge only for it to be rejected understandably since there was a spelling difference between my answer and the challenges’ answer.

When I check the solution, I found the differences of my code vs solution code minuscule. So I went and made some modifications to my code only for it to return an empty array.

Code[a] is my first answer.
Code[b] is my revised answer which is returning an empty array
Code[c] is the solution.

This is a sort to deeply understand the fundamentals etc.

Q. May you please explain why is that, when I change the key of Code[a] to Code[b]. An empty array is returned?
Please notice that Code[b] and Code[c] are identical except for the order of which they are executed.

FYI The key in question is the imdbRating key vs rating

Your code so far

const filteredList = watchList
.map(({Title: title, imdbRating: imdbRating}) => ({title, imdbRating}))
.filter((item) => item.imdbRating >= 8.0)

const filteredList = watchList
.map(({Title: title, imdbRating: rating}) => ({title, rating}))
.filter((item) => item.imdbRating >= 8.0)

const filteredList = watchList
  .filter(({ imdbRating }) => imdbRating >= 8.0)
  .map(({ Title: title, imdbRating: rating }) => ({ title, rating }))

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/100.0.4896.127 Safari/537.36

Challenge: Use the filter Method to Extract Data from an Array

Link to the challenge:

Take a closer look at the difference between Code[a] and Code[b] before arrays are filtered:

const filteredList = watchList
.map(({Title: title, imdbRating: rating}) => ({title, rating}))

map, for each element returns object having title and rating properties. At the next step, with filter, filtering function is expecting imdbRating property.


HI @P.Mat3 !

If you want a visual of what @sanity has brought up, temporarily comment out your filter function and see what is returned in the console.

const filteredList = watchList
.map(({Title: title, imdbRating: rating}) => ({title, rating}))
//  .filter((item) => item.imdbRating >= 8.0)

Then you can see why you are getting an empty array using filter.

1 Like

@jwilkins.oboe Thank you to the both of you. It’s these little mistakes that do not get repeated once I understand what I did wrong. Most times another set of eyes is better that one.

Until next time.

1 Like

Item is undefined
Hence empty array

There is difference between code [c] and b

Item is a place holder of the item being iterated through. Item is defined. BTW, this issue has been resolved. You can find the solution above.

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