using map with filter array JavaScript

Question

i have a json and need to extract data to array.

const data = [{
  "week": 1,
  "lost": 10,
  "recovery_timespan": [{
    "week": 2,
    "count": 1
  }, {
    "week": 3,
    "count": 0
  }],
   "netLost": 10,
  "netReturned": 20
}, {
  "week": 2,
  "lost": 7,
  "recovery_timespan": [{
    "week": 3,
    "count": 1
  }],
  "netLost": 30,
  "netReturned": 200
}, {
  "week": 3,
  "lost": 8,
  "recovery_timespan":"",
  "netLost": 50,
  "netReturned": 40
}];

Expected output: lost,count in recovery_timespan,netLost , netReturned.

[ [ 10, 1, 0, 10, 20 ], [ 7, 1, 30, 200 ], [ 8, 50, 40 ] ]

As you can see expected output, last recovery_timespan does not contain any data and it just shows as "".so i need to ignore it.

My approach:

const result = data.map(({lost, recovery_timespan,netLost,netReturned}) => [
  lost,
  ...recovery_timespan.map(({count}) => count),
  netLost,netReturned
]);

My code breaks when "recovery_timespan" is "". How can i add a filter along with map to filter that part and make my code work?

Want to skip records when recovery_timespan is empty?

Arup Rakshit
– Arup Rakshit

2022-10-10 18:31:15 +00:00
Commented Oct 10, 2022 at 18:31 — Arup Rakshit
– Arup Rakshit, Commented Oct 10, 2022 at 18:31
yes, my code breaks when there is "" for recovery_timespan.

Adam
– Adam

2022-10-10 18:42:54 +00:00
Commented Oct 10, 2022 at 18:42 — Adam
– Adam, Commented Oct 10, 2022 at 18:42

IT goldman · Accepted Answer · 2022-10-10 18:31:57Z

3

It's just a matter of checking if it's string or not, but you can short circuit

const result = data.map(({lost, recovery_timespan,netLost,netReturned}) => [
  lost,
  ...(recovery_timespan || []).map(({count}) => count),
  netLost,netReturned
]);

answered Oct 10, 2022 at 18:31

IT goldman

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2 Comments

Adam Over a year ago

this works. Can you please explain recovery_timespan || [ ] part?

IT goldman Over a year ago

it's a classic (although not necessarily precise) shortcut because OR expressions are evaluated left to right and in a lazy way. That means if recovery_timespan is truthy then it won't even get to evaluate the [] part. However, if recovery_timespan is falsy then the second part of the expression will evaluate to return the result []. falsy is 0, "", false etc

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