# Help with No Repeats Please Algorithm

Hi all, I’m having some trouble with this challenge. Here’s my code:

``````function permAlone(str) {
var arr = str.split("");
var numArr = [];
var permArr = [];
var permutation = 1;
arr.forEach(function(value, index) {
permutation = permutation * (index+1);
numArr.push(index+1);
});
var reString = numArr.join("");
var first = numArr;
var last = numArr[numArr.length-1];
var re = new RegExp("^" + ("[" + first + "-" + last + "]").repeat(numArr.length) + "\$","g");
var num = reString * numArr.length;

function hasRepeatedNumbers(repeatNum) {
repeatNum = repeatNum.toString().split("").sort().join("");
var patt = new RegExp(/([0-9])\1+/,"g");
var result = patt.test(repeatNum);
return result;
}

var x = num;
while (x > 0) {
if (re.test(x) && !(hasRepeatedNumbers(x))) {
permArr.push(x);
}
x--;
}

return permArr;
}

permAlone('aabb');
``````

I attempted to switch up the strings into numbers and then find all permutations of those numbers. Currently my loop only pushes 13 numbers into my array. I can’t seem to understand why it’s not recognizing the other 3. Any help would be greatly appreciate.

Thanks!

It looks like the issue has to do with Regular expression test() method, but I haven’t figured the real reason yet and how test() really actually works…, I went on MDN and found this mysterious excerpt (hopefully you will help me understand) :

As with exec() (or in combination with it), test() called multiple times on the same global regular expression instance will advance past the previous match.

So, I changed one line.

``````function permAlone(str) {
var arr = str.split("");
var numArr = [];
var permArr = [];
var permutation = 1;
arr.forEach(function(value, index) {
permutation = permutation * (index+1);
numArr.push(index+1);
});
var reString = numArr.join("");
var first = numArr;
var last = numArr[numArr.length-1];
// var re = new RegExp("^" + ("[" + first + "-" + last + "]").repeat(numArr.length) + "\$","g");
var num = reString * numArr.length;

function hasRepeatedNumbers(repeatNum) {
repeatNum = repeatNum.toString().split("").sort().join("");
var patt = new RegExp(/([0-9])\1+/,"g");
var result = patt.test(repeatNum);
return result;
}

var x = num;
while (x > 0) {
if (new RegExp("^" + ("[" + first + "-" + last + "]").repeat(numArr.length) + "\$","g").test(x) // replaced "re" with a newly created RegExp
&& !(hasRepeatedNumbers(x))) {
permArr.push(x);
}
x--;
}

return permArr;
}

permAlone('aabb');
``````

Is that result what you expected ? :

update: I found a resource that I hope will help you : http://stackoverflow.com/questions/1520800/why-regexp-with-global-flag-in-javascript-give-wrong-results
Apparently, removing the “g” flag in RegExp() will fix this.

That’s it exactly. Thanks for the help!