No Repeats please with string solution

I did not read all solution but as I seen everyone resolved this challenge with array.
My solution is working with string…
In guide topic the regEx code is really elegant,

var regex = /(.)\1+/;

unfortunately I did not find this easy code, my regex is more complex, but still works…
My solution:

function permAlone(str) {
    if (str.length < 2) return str.length;
    const uniqueArray = dirtyArray => dirtyArray.filter((value, index, array) => array.indexOf(value) === index);
    const uniqueChars = uniqueArray([...str]);
    const permFunc = (str) => {
        // if (str.length < 2) return str;

        const permutation = []; // This array will hold our permutations

        for (let i = 0; i < str.length; i ++) {
            const char = str[i];
            const remainingString = str.slice(0, i) + str.slice(i + 1, str.length);
            for (let subPermutation of permFunc(remainingString)) {
                permutation.push(char + subPermutation);
        return permutation;
    let permutations = permFunc(str);
    let regEx = new RegExp(`${uniqueChars.join("{2}|")}{2}`);
    permutations = permutations.filter(value => !(regEx.test(value)));
    return permutations.length;

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