How to split last n digits of each value in the array with JavaScript?

We have an array of literals like this −

const arr = ["", 20191219, 20191220, 20191221, 20191222, 20191223, 20191224, 20191225];

We are required to write a JavaScript function that takes in this array and a number n and if the corresponding element contains more than or equal to n characters, then the new element should contain only the last n characters otherwise the element should be left as it is.

Let's write the code for this function −

Example

const arr = ["", 20191219, 20191220, 20191221, 20191222, 20191223, 20191224, 20191225]; const splitElement = (arr, num) => {    return arr.map(el => {       if(String(el).length <= num){          return el;       };       const part = String(el).substr(String(el).length - num, num);       return +part || part;    }); }; console.log(splitElement(arr, 2)); console.log(splitElement(arr, 1)); console.log(splitElement(arr, 4));

Output

The output in the console will be −

[    '', 19, 20, 21,    22, 23, 24, 25 ] [    '', 9, '0', 1,    2, 3, 4, 5 ] [    '', 1219, 1220,    1221, 1222, 1223,    1224, 1225 ]