how to access nested array/object and filter non empty elements of array like NaN,null,0

Question

Below is the array of objects. what we have to do is to

create an array that contains all the non-empty elements of array arr with value not equal to null, NaN, 'undefined' and 0
remaining in the second array

var arr = [
  { id: 15 },
  { id: -1 },
  { id: 0 },
  { id: 3 },
  { id: 12.2 },
  {},
  { id: null },
  { id: NaN },
  { id: "undefined" }
];

what I have tried is


var obj1 = {};
 var prop1 = [];
 var prop2 = [];
  arr.forEach(el=>{
      if(el.id!==0 || el.id!==null || el.id!==undefined || el.id!==NaN){
          prop1.push(el)
      }
      else{
          prop2.push(el)
      }
  })
  console.log(prop1)
  
  console.log(prop2)

but it is not working

output I receive -

1] [{id: 15}, {id: -1}, {id: 0}, {id: 3}, {id: 12.2}, {}, {id: null}, {id: null}, {id: "undefined"}]

2] []

expected -

1] [{id: 0}, {id: null}, {id: "undefined"}]

2] [{id: 15}, {id: -1}, {id: 3}, {id: 12.2}]

Please add what you are getting as an output when you console.log(prop1) and prop2 — noahdubs
– noahdubs, Commented Apr 7, 2020 at 3:38
Instead of writing "it is not working", please describe in detail what the expected outcome vs. actual outcome is. If you get any errors list them explicitly. — Wyck
– Wyck, Commented Apr 7, 2020 at 3:40
Think about all the things that satisfy (x !== 0 || x != null) You are currently thinking about all things. ;) You likely intended && instead of ||. — Wyck
– Wyck, Commented Apr 7, 2020 at 3:42
Do you understand why el.id!==0 || el.id!==null || el.id!==undefined || el.id!==NaN will always be true? Consider: (x !== 1 || x !== 2) You meant &&. — Wyck
– Wyck, Commented Apr 7, 2020 at 3:47
Did you REALLY mean to include the string "undefined" or did you just mean undefined? That seems a little bit weird. — Wyck
– Wyck, Commented Apr 7, 2020 at 3:54

mickl · Accepted Answer · 2020-04-08 01:27:33Z

2

You can cast to boolean (!el.id) which will handle most cases and you have to deal with "undefined" separately:

var arr = [
  { id: 15 },
  { id: -1 },
  { id: 0 },
  { id: 3 },
  { id: 12.2 },
  {},
  { id: null },
  { id: NaN },
  { id: "undefined" }
];

var obj1 = {};
 var prop1 = [];
 var prop2 = [];
  arr.forEach(el=>{
      if(!el.id || el.id === "undefined"){
          prop1.push(el)
      }
      else{
          prop2.push(el)
      }
  })

  console.log(prop1);
  console.log(prop2);
  console.log(prop1.length);
  console.log(prop2.length);

edited Apr 8, 2020 at 1:27

answered Apr 7, 2020 at 3:39

mickl

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1 Comment

mickl Over a year ago

It's all fine. prop2 represents non-empty elements so the count that gets returned is 4, whereas prop1.length returns 5 (you can run my script to see that)

LearningEveryday · Accepted Answer · 2020-04-07 03:48:53Z

1

Try this:

var arr = [
  { id: 15 },
  { id: -1 },
  { id: 0 },
  { id: 3 },
  { id: 12.2 },
  {},
  { id: null },
  { id: NaN },
  { id: "undefined" }
];
let filterArray = arr.filter((el) => {return !el.id || [0,null,"undefined",NaN].includes(el.id)});
console.log(filterArray);
let filterArray1 = arr.filter((el) => {return el.id && ![0,null,"undefined",NaN].includes(el.id)});
console.log(filterArray1);

edited Apr 7, 2020 at 3:48

answered Apr 7, 2020 at 3:37

LearningEveryday

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2 Comments

LearningEveryday Over a year ago

Edited to use .includes as we can add what we want in it for ease.

LearningEveryday Over a year ago

Edited further to handle blank entry!

Markus Anetz · Accepted Answer · 2020-04-07 03:40:51Z

0

why does it not work? Is the ordering incorrect or is there a JavaScript error?

The code looks fine at the first glance, you may use if (!el.id), which checks if the id is "falsy" (0, null, undefined, NaN, false)

You may also have a look at the methods "map" and "filter", https://developer.mozilla.org/de/docs/Web/JavaScript/Reference/Global_Objects/Array/filter

https://developer.mozilla.org/de/docs/Web/JavaScript/Reference/Global_Objects/Array/map

answered Apr 7, 2020 at 3:40

Markus Anetz

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