Fill empty values of a nested array with specific value Javascript-CodePudding

I have a function called Action which receives an array parameter like this.

[
  ['X','','O'],
  ['O','','O'],
  ['X','X','']
]

I want this function to return an array like this where each empty section of the previous array is filled individually with a specific value, e.g Y.

[
 [
   ['','Y',''],
   ['','',''],
   ['','','']
 ],
 [
   ['','',''],
   ['','Y',''],
   ['','','']
 ],
 [
   ['','',''],
   ['','',''],
   ['','','Y']
 ]

]

I know I can do that with forEach but it needs nested forEach which I think isn't very optimal. Is there any better way of doing that?

CodePudding user response：

This should work:

let arr = [
  ['X','','O'],
  ['O','','O'],
  ['X','X','']
]

let res = []

arr.map((item, index)=>{
    item.map((sub, indx) =>{
        if(sub === ""){
        let array_=
            [
               ['','',''],
               ['','',''],
               ['','','']
             ];

             array_[index][indx] = "Y";

             res.push(array_)

        }
    })
})

console.log(res)

CodePudding user response：

You could avoid nesting loops with the following steps

flatten the matrix into a 1-d array
get the indices of the empty sections
create new flatten 1-d arrays with empty indices from previous result marked as 'Y'
transform flatten 1-d arrays back to 3x3 matrix

const arr = [
  ["X", "", "O"],
  ["O", "", "O"],
  ["X", "X", ""],
]

const res = arr
  .flat() // flatten the array
  .map((section, i) => [section, i])
  .filter(([section, _]) => section === "")
  .map(([_, i]) => i) // get the indices of empty sections
  .map(sectionIdx =>
    Array.from({ length: 9 }, (_, i) => (i === sectionIdx ? "Y" : ""))
  ) // create new flattened array with empty indices marked as 'Y'
  .map(flattenedArr => [
    flattenedArr.slice(0, 3),
    flattenedArr.slice(3, 6),
    flattenedArr.slice(6, 9),
  ]) // turn back flatten array into 3x3 matrix

console.log(res)