uncompress bfe.dev solution in javaScript

uncompress-bfe.dev.js

function uncompress(str) {
    var result = str;

    while (/\d/.test(result)) {
        var start = result.lastIndexOf("(")
        var end = result.indexOf(")")

        var rounds = parseInt(result[start - 1], 10);

        var repeats = result.substring(start + 1, end).repeat(rounds)

        result = result.substring(0, start - 1) + repeats + result.substring(end + 1, result.length)
    }

    return result;
}

Test cases
var input = "3(ab)"
var expectedAnswer = "ababab";
console.log(uncompress(input) === expectedAnswer);

var input = "3(ab2(c))"
var expectedAnswer = "abccabccabcc";
console.log(uncompress(input) === expectedAnswer);

var input = "2(ab2(a2(b)))"
var expectedAnswer = "ababbabbababbabb";
console.log(uncompress(input) === expectedAnswer);