# Function to decode a string in JavaScript

JavascriptWeb DevelopmentFront End TechnologyObject Oriented Programming

We are given an encoded string, and we are required to process it through a function that returns its decoded string.

The encoding rule is −

n[encodedString], where the encodedString inside the square brackets is being repeated exactly n times.

And n is guaranteed to be a positive integer.

We can assume that the input string is always valid; No extra white spaces, square brackets are well−formed, etc.

For example − If the input is −

const str = "3[a]2[bc]";

Then the output should be −

const output: "aaabcbc";

## Example

The code for this will be −

const str = "3[a]2[bc]";
const helper = (str = '') => {
return str.replace(/(\d+$\w+$)/gi, item => {
let match = /(\d+)$(\w+)$/.exec(item);
let repeat = parseInt(match[1]);
let pattern = match[2];
let result = "";
while(repeat−− > 0) {
result += pattern;
}
return result;
});
};
const decodeString = function(str) {
while(/\d+$\w+$/gi.test(str)) {
str = helper(str);
}
return str;
};
console.log(decodeString(str));

## Output

And the output in the console will be −

aaabcbc
Published on 23-Nov-2020 11:09:39