Find list of empty indices in a javascript array

Question

Is there a way in Javascript to find the indices where an array is empty or doesnt contain "x"?

["x", "", "", "x", "", "", ""]

Would return something like:

[1,2,4,5,6]

I have attempted something like this:

empty = roster.findIndex((obj) => Object.keys(obj).length === 0)

However I can't come up with a way to iterate over the list.

Answer 1

 const arr = ['x', '', '', 'x', '', '', '']; const emptyIndexes = arr.reduce((acc, curr, index) => { if (curr === '') { acc.push(index); } return acc; }, []); console.log(emptyIndexes);

Answer 2

 roster = ["x", "", "", "x", "", "", ""] emptyIndexArray = [] for (i = 0; i < roster.length; i++) { if (roster[i] === "") { emptyIndexArray[emptyIndexArray.length] = i; } } emptyIndexArray.forEach(x => console.log(x));

Answer 3

arr.map((item, index) => item === '' ? index : null).filter(item => item)

Answer 4

Well here is another approach based on character codes.

const removeSpaceDuplicates = (arr) => {
  var result = []

  for(let i = 0; i < arr.length; i++){
    var x = "x".charCodeAt(0),
        empty = isNaN(arr[i].charCodeAt(0)),
        cur =  arr[i].charCodeAt(0)
    
    if( cur == empty || cur != x){
      result.push(i)
    }
  }
  
  return result
}



//====>  [1, 2, 4, 5, 6]

Answer 5

It's not going to be length == 0 right, you want empty or doesn't contain x Also find index returns the first index that match, you have to do a map.

See this solution here: EcmaScript6 findIndex method, can it return multiple values?

Recap:

let roster = ["x", "", "", "x", "", "", ""];
let indexes = ages.map((elm, idx) => (elm == '' || elm != 'x') ? idx : '').filter(String);
console.log( indexes );