ordered permutations

function powerSet(list) {

    var set = [];
    var listSize = list.length;
    var combinationsCount = 1 << listSize;
    var combination;
    var i = 1;
    var j;
    
    for(; i < combinationsCount; i++ ) {
        var combination = [];
        for(j=0; j<listSize; j++) {
            if(i & 1 << j){
                combination.push(list[j]);
            }
        }
        set.push(combination);
    }
    
    return set;
}

console.log(powerSet(['a','b','c','d']))