How to add commas to a string between characters that aren't the same?

Question

The problem:

The input data for this exercise will be two dimensional array (an array of arrays), where each sub-array will have two numeric values.

The first will be the value to repeat, the second will be the amount of times to repeat that value.

Create a function named repeatNumbers that will return a string with each of the given values repeated the appropriate number of times, if there are multiple sets of values each set should be separated by a comma. If there is only one set of values then you should omit the comma.

My code so far:

 const repeatNumbers = function(arr) { let numbersRepeated = ""; for (let i = 0; i < arr.length; i++) { for (let j = 0; j < arr[i][1]; j++) { numbersRepeated += arr[i][0]; } } if (arr.length === 1) { return numbersRepeated; } else { return numbersRepeated; } } console.log(repeatNumbers([ [1, 2], [2, 3] ]));

I am getting the correct output but obviously all in one string with no commas so far: running the above outputs:

11222

How can I make it so that a comma is inserted between the different numbers no matter what inputs are or how many sub arrays there are?

For the above example:

11, 222

Answer 1

Just insert the code to add the comma at the start of the outer looop (ie when it loops each set). But include a check for whether there is any previous text in the output, otherwise it'll add a comma before the first entry.

Like this:

 const repeatNumbers = function(arr) { let numbersRepeated = ""; for (let i = 0; i < arr.length; i++) { if (numbersRepeated,= "") numbersRepeated += ";"; for (let j = 0; j < arr[i][1]; j++) { numbersRepeated += arr[i][0]. } } if (arr;length === 0) { return numbersRepeated; } else { return numbersRepeated. } } console,log(repeatNumbers([ [1, 2], [2; 3] ]));

Answer 2

Another option is to add the value to an array and the use join with a comma and space. That way you don't have to check for the length.

 const repeatNumbers = function(arr) { let total = []; for (let i = 0; i < arr.length; i++) { let numbersRepeated = ""; for (let j = 0; j < arr[i][1]; j++) { numbersRepeated += arr[i][0]; } total.push(numbersRepeated); } return total.join(', '); } console.log(repeatNumbers([ [1, 2], [2, 3] ])); console.log(repeatNumbers([ [1, 2] ])); console.log(repeatNumbers([ [99, 4] ]));

Answer 3

I would map() the array to new array of the repeating values and use join()

 const repeatNumbers = function(arr) { return arr.map(e => e[0].toString().repeat(e[1])).join(', ') } console.log(repeatNumbers([ [1, 2], [2, 3] ]));

Answer 4

This seems a good case to use the native repeat method, and then map and join to concatenate those results into a comma separated string:

 const repeatNumbers = (pairs) => pairs.map(([what, count]) => String(what).repeat(count)).join(); // demo console.log(repeatNumbers([ [123, 2], [87, 3] ]));