How to change the values of a nested array to all same string?

Question

I would like to change a nested array that contains a * to all the same * values . For instance, this grid

  ["A", "*", "C"],
  ["D", "E", "p"],
  ["G", "H", "I"],

Would turn into

  ["*", "*", "*"],
  ["D", "E", "p"],
  ["G", "H", "I"],

Here is my function so far:

function changeArr(grid) {
    for (let arr of grid) {
        if (arr.includes("*")) {
            arr.forEach(element => element = "*")
        }
    }
    return grid;
}

My function just returns the same initial grid that was passed through the function. I've also tried

function changeArr(grid) {
    for (let arr of grid) {
        if (arr.includes("*")) {
            arr.splice(0, 3, ["*","*","*"])
        }
    }
    return grid;
}

But this creates a nested array within a nested array! I feel like this can be easily accomplished with a forEach but not sure how.

While it's not an extremely nice code, your attempt with splice() should work after you remove the brackets, so arr.splice(0, 3, "*", "*", "*"); remains. — tevemadar
– tevemadar, Commented Nov 2, 2020 at 23:51

Emilio Grisolía · Accepted Answer · 2020-11-02 23:54:28Z

Inside the forEach, you are not really modifying the array. You are passing a value to forEach, corresponding to the values of the nested array. So when you change element's variable value, you are just changing it inside the forEach callback.

There are a few ways to do this... you can go something like this.

    let array = [
        ['A', '*', 'C'],
        ['A', 'B', 'C']
    ]
    
    for (let nestedArray of array) {
        if (nestedArray.includes('*')) {
            for (let i = 0; i < nestedArray.length; i++) nestedArray[i] = '*';
        }
    }
    
    console.log(array);

Or go by using splice if they all have the same fixed size (or even reassign the nestedArray to a ['*', '*', '*']).

Just to be clear: If you have this array: ['a', 'b', 'c']

And iterate it with forEach:

array.forEach(element => ...)

element will have the values 'a', 'b', 'c'. But those are NOT the same 'a', 'b', 'c' of the array. They are copies. So reassigning element to another value, won't affect the original array.

Dozer · Accepted Answer · 2020-11-02 23:48:11Z

1

This is my solution, a function that iterates through the array and find the nested array which contains * and then replace its values

var grid = [
  ['A', '*', 'B'],
  ['C', 'D', 'E'],
  ['H', 'G', 'F']
]

function changeArr(grid) {
  grid.forEach(arr => {
    if (arr.includes('*')) {
      for (var i = 0; i < arr.length; i++) {
        arr.splice(i, i, '*');
      }
    }
  })
}

console.log(grid);
changeArr(grid);
console.log(grid);

answered Nov 2, 2020 at 23:48

Dozer

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