Replacing all elements in a nested Array

Question

I have a challenge that I have been battling with for some time now. It's about replacing all the elements in an array that is in a grid form, but my solution is only replacing selected element of its choice not as I intended.

In this challenge, I want to replace the integer value that is divisible by two with the string "even" while the rest replaced with the string "odd".

/* * - The numbers variable is an array of arrays. * - a nested for loop to cycle through numbers. * - it convert each even number to the string "even" * - and Convert each odd number to the string "odd" */

var myNumbers = [
 [243, 12, 23, 12, 45, 45, 78, 66, 223, 3],
 [34, 2, 1, 553, 23, 4, 66, 23, 4, 55],
 [67, 56, 45, 553, 44, 55, 5, 428, 452, 3],
 [12, 31, 55, 445, 79, 44, 674, 224, 4, 21],
 [4, 2, 3, 52, 13, 51, 44, 1, 67, 5],
 [5, 65, 4, 5, 5, 6, 5, 43, 23, 4424],
 [74, 532, 6, 7, 35, 17, 89, 43, 43, 66],
 [53, 6, 89, 10, 23, 52, 111, 44, 109, 80],
 [67, 6, 53, 537, 2, 168, 16, 2, 1, 8],
 [76, 7, 9, 6, 3, 73, 77, 100, 56, 100]
];
for(var row=0; row<myNumbers.length; row++) {
 for(var column=0;column<myNumbers[row].length;column++) {
 if(myNumbers[column]%2===0){
 myNumbers[column].splice(column,1,"even");
 }else{ 
 myNumbers[column].splice(column,1,"odd");
 }
 console.log(myNumbers[row][column]);
 }
} 

Code Output: 

 odd 12 23 12 45 45 78 66 223 3 34 odd 1 553 23 4 66 23 4 55 67 56 odd 553 44 55 5 428 452 3 12 31 55 odd 79 44 674 224 4 21 4 2 3 52 odd 51 44 1 67 5 5 65 4 5 5 odd 5 43 23 4424 74 532 6 7 35 17 odd 43 43 66 53 6 89 10 23 52 111 odd 109 80 67 6 53 537 2 168 16 2 odd 8 76 7 9 6 3 73 77 100 56 odd

Answer 1

You used the wrong variable for the row index

myNumbers[column]
//needs to be
myNumbers[row]

Also your if condition is using the wrong row index, and trying to compare against the whole array instead of the value in the array

if(myNumbers[column]%2===0)
//needs to be
if(myNumbers[row][column]%2===0)

Demo

var myNumbers = [
 [243, 12, 23, 12, 45, 45, 78, 66, 223, 3],
 [34, 2, 1, 553, 23, 4, 66, 23, 4, 55],
 [67, 56, 45, 553, 44, 55, 5, 428, 452, 3],
 [12, 31, 55, 445, 79, 44, 674, 224, 4, 21],
 [4, 2, 3, 52, 13, 51, 44, 1, 67, 5],
 [5, 65, 4, 5, 5, 6, 5, 43, 23, 4424],
 [74, 532, 6, 7, 35, 17, 89, 43, 43, 66],
 [53, 6, 89, 10, 23, 52, 111, 44, 109, 80],
 [67, 6, 53, 537, 2, 168, 16, 2, 1, 8],
 [76, 7, 9, 6, 3, 73, 77, 100, 56, 100]
];
for (var row = 0; row < myNumbers.length; row++) {
 for (var column = 0; column < myNumbers[row].length; column++) {
 if (myNumbers[row][column] % 2 === 0) {
 myNumbers[row].splice(column, 1, "even");
 } else {
 myNumbers[row].splice(column, 1, "odd");
 }
 }
}
console.log(myNumbers);

• Ajiroghene: I agree with you completely. Thanks

Answer 2

Probably easier to use a nested map instead:

var myNumbers = [
 [243, 12, 23, 12, 45, 45, 78, 66, 223, 3],
 [34, 2, 1, 553, 23, 4, 66, 23, 4, 55],
 [67, 56, 45, 553, 44, 55, 5, 428, 452, 3],
 [12, 31, 55, 445, 79, 44, 674, 224, 4, 21],
 [4, 2, 3, 52, 13, 51, 44, 1, 67, 5],
 [5, 65, 4, 5, 5, 6, 5, 43, 23, 4424],
 [74, 532, 6, 7, 35, 17, 89, 43, 43, 66],
 [53, 6, 89, 10, 23, 52, 111, 44, 109, 80],
 [67, 6, 53, 537, 2, 168, 16, 2, 1, 8],
 [76, 7, 9, 6, 3, 73, 77, 100, 56, 100]
];
const output = myNumbers.map(row => row.map(num =>
 num % 2 === 0
 ? 'even'
 : 'odd'
));
console.log(output);

Achieving the same thing with a for loop is much more verbose and confusing, and shouldn't be done in most cases (array methods have better abstraction and don't require manual iteration), but if necessary:

var myNumbers = [
 [243, 12, 23, 12, 45, 45, 78, 66, 223, 3],
 [34, 2, 1, 553, 23, 4, 66, 23, 4, 55],
 [67, 56, 45, 553, 44, 55, 5, 428, 452, 3],
 [12, 31, 55, 445, 79, 44, 674, 224, 4, 21],
 [4, 2, 3, 52, 13, 51, 44, 1, 67, 5],
 [5, 65, 4, 5, 5, 6, 5, 43, 23, 4424],
 [74, 532, 6, 7, 35, 17, 89, 43, 43, 66],
 [53, 6, 89, 10, 23, 52, 111, 44, 109, 80],
 [67, 6, 53, 537, 2, 168, 16, 2, 1, 8],
 [76, 7, 9, 6, 3, 73, 77, 100, 56, 100]
];
const output = [];
for (let rowIndex = 0; rowIndex < myNumbers.length; rowIndex++) {
 const row = myNumbers[rowIndex];
 const newRow = [];
 for (let colIndex = 0; colIndex < row.length; colIndex++) {
 const num = row[colIndex];
 newRow.push(num % 2 === 0 ? 'even' : 'odd');
 }
 output.push(newRow);
}
console.log(output);

• user7148391: i'm confused to why this is working, shouldn't there be a return statement ?
• Ajiroghene: Wow, but this seems too advanced to grasp. Please come down to my level. Can you break it down first using my beloved nested for, thereafter this advanced method...
• CertainPerformance: @ZohirSalakCeNa Arrow functions without { blocks have implicit return.
• user7148391: Oh i see now, i still only use function(){}, Thanks :)

Answer 3

Why not simply set the value of myNumbers[row][column] instead of using splice?

var myNumbers = [
 [243, 12, 23, 12, 45, 45, 78, 66, 223, 3],
 [34, 2, 1, 553, 23, 4, 66, 23, 4, 55],
 [67, 56, 45, 553, 44, 55, 5, 428, 452, 3],
 [12, 31, 55, 445, 79, 44, 674, 224, 4, 21],
 [4, 2, 3, 52, 13, 51, 44, 1, 67, 5],
 [5, 65, 4, 5, 5, 6, 5, 43, 23, 4424],
 [74, 532, 6, 7, 35, 17, 89, 43, 43, 66],
 [53, 6, 89, 10, 23, 52, 111, 44, 109, 80],
 [67, 6, 53, 537, 2, 168, 16, 2, 1, 8],
 [76, 7, 9, 6, 3, 73, 77, 100, 56, 100]
];
 for(var row=0; row<myNumbers.length; row++) {
 for(var column=0;column<myNumbers[row].length;column++) {
 if(myNumbers[row][column]%2===0) {
 myNumbers[row][column] = "even";
 } else{ 
 myNumbers[row][column] = "odd";
 }
 console.log(myNumbers[row][column]);
 }
 }

• Ajiroghene: Wow, I'd never thought of it this way. I am going right away to implement this.
• C0D3JUNKIE: This is the most straight forward way to perform the replace or by using the splice method noted by @Patrick Evans. Thanks xrisk

Answer 4

In your inner loop you need to access the values using both indexes (i.e. myNumbers[row][column]). As it stands, you are only using the column index and therefore splicing values into the array containing the rows.