Quick sketch code spiral output matrix...

p_200.js

const c = console.log.bind(console)

let arr_0 = [
    [1, 2, 3, 10], 
    [4, 5, 6, 11], 
    [7, 8, 9, 11],
    [12, 13, 14, 15]
]

let arr_1 = [
    [18, 19, 20, 21]
]

let arr_2 = [
    [30],
    [21],
    [45],
    [34]
]

let arr_3 = [
    [84]
]

let arr_4 = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
]

let arr_5 = [
    [1, 2, 3, 10], 
    [4, 5, 6, 11], 
    [7, 8, 9, 11],
    [12, 13, 14, 15]
]

let arr_6 = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
]


spiral_read_outside_mat(arr_0)
mat_strip_border(arr_0)
c('\n')
spiral_read_outside_mat(arr_0)

c('\n')
spiral_read_outside_mat(arr_1)

c('\n')
spiral_read_outside_mat(arr_2)

c('\n')
spiral_read_outside_mat(arr_3)

c('\n')
spiral_read_outside_mat(arr_4)

c('\n \n \n Real Test:')

spiral_read_mat(arr_5)

c('\n \n \n Real Test 2:')

spiral_read_mat(arr_6)


function spiral_read_mat(arr) {
    // edge cases:
    // the matrix cull might leave a single row or column vector, in that case we wouldn't want to run all
    // of these things

    // we definitely do the top row to the right.  if this is the only element in the mat we done.
    // if col_len > 1 we can do the down column part

    // the route back only happens if row_len > 1
    // and the route back up will happen also if row_len > 1

    while (arr.length > 0 && arr[0].length > 0) {
        spiral_read_outside_mat(arr)
        mat_strip_border(arr)
    }

}

function mat_strip_border(arr) {
    arr.splice(0, 1)
    arr.splice(arr.length - 1, 1)
    
    arr.map((row) => {
        row.splice(0, 1)
        row.splice(row.length - 1, 1)
    })
}


function spiral_read_outside_mat(arr) {
    
    let row_len = arr[0].length
    let column_len = arr.length

    for (let i = 0; i < row_len; i++) {
        c(arr[0][i])
    }

    for (let j = 1; j < column_len; j++) {
        c(arr[j][row_len - 1])
    }

    if (row_len > 1 && column_len > 1) {
        for (let i = (row_len - 2); i > -1; i--) {
            c(arr[column_len - 1][i])
        }
    
        for (let j = column_len - 2; j > 0; j--) {
            c(arr[j][0])
        }

    }

}