Masking a string JavaScript

We are required to write a JavaScript function that takes in string value as the first argument and a pattern string as the second argument.

Suppose the string and the pattern are −

const str = '123456789';
const pattern = '## ## ## ###';

Then the function should pad the string according to the pattern and the output string should be −

const output = '12 34 56 789';

Example

const str = '123456789';
const pattern = '## ## ## ###';
const maskString = (str, pattern) => {
   let i = 0;
   const padded = pattern.replace(/#/g, () => {
      return str[i++];
   });
   return padded;
};
console.log(maskString(str, pattern));

Output

And the output in the console will be −

12 34 56 789