Generate the powerset of a given string

powerSet.js

function powerSet(str) {
    var chars = str.split("");
    var result = [""];
    chars.forEach(function(v){
        var newResult = [];
        result.forEach(function(item) {
            newResult.push(item+v);
        });
        result = result.concat(newResult);
    });
    return result;
}
powerSet("abcd");