An algorithm that prints all permutations of a string

permutateString.js

/**
* Returns an array of strings, with different positions of char in the string - str
*/
function swapAll(str, char) {
    const result = [];
    for (let i = 0; i <= str.length; i += 1) {
        const newStr = `${str.slice(0, i)}${char}${str.slice(i, str.length)}`;
        result.push(newStr);
    }
    return result;
}

/**
* A function that prints all permutations of a string
*/
function permutate(str, arr=[], level=1) {
    if (level >= str.length) {
        return arr;
    } else {
        if (arr.length <= 0) {
            const substr = str.substring(0, level);
            const newArr = swapAll(substr, str[level]);
            return permutate(str, newArr, level + 1);
        } else {
            let newArr = [];
            arr.forEach((permutedStr) => {
                const swaps = swapAll(permutedStr, str[level]);
                newArr = [...newArr, ...swaps];
            });
            return permutate(str, newArr, level + 1);
        }
    }
}

// Example:
permutate('abc'); // ['cba', 'bca', 'bac', 'cab', 'acb', 'abc']