LOGIC ERROR: Converting Python to JavaScript. Code runs, but gives wrong answer

I started learning JavaScript 4 days ago and I am trying to convert my python project to JavaScript for practice.

Here is my working python code:

def shuffle(l):
    for shuffles in range(numPerformed):
        heads = 0
        #tails = 0 
        toss = []
        for card in range(numCards):
            x = np.random.randint(2)
            toss.append(x)
            if x == 0:
                heads += 1
            #else:
                #tails += 1
        
        left = l[:heads] #left hand
        right = l[heads:] #right hand
        shuffled = []   #shuffled deck
        
        for card in range(numCards):
            if toss[card] == 0:
                shuffled.append(left.pop(0))
            if toss[card] == 1:
                shuffled.append(right.pop(0))
        l = shuffled
    return l

numCards = int(input("Enter number of cards in deck: "))
l = list(range(numCards))
numPerformed = int(input("Enter number of shuffles to perform on deck: "))
print(shuffle(l))

I am using the coin-toss method to do riffle shuffle. Here is my JS code, but something is causing it to give the wrong answer:

const list = (numCards) => {
    var newList = []
    var i = 0;
    while (i < numCards){
        newList.push(i);
        i++;
    }
    return newList
}

function shuffle(l, numPerformed){
    for (var shuffles = 0; shuffles < numPerformed; shuffles++){
        var heads = 0;
        var tails = 0;
        var toss = [];
        for (var card = 0; card < l.length; card++){
            var x = Math.floor(Math.random() * 2);
            toss.push(x);
            if (x == 0){
                heads++;
            }else{
                tails++;
            }
        }
        var left = []; //l[:heads]
        var right = []; //l[heads:]
        for (var i = 0; i < l.length; i++){
            i < heads ? left.push(i) : right.push(i);
        }

        var shuffled = [];
        for (var card = 0; card < numCards; card++){
            if (toss[card] == 0){
                shuffled.push(left.shift());
            }else if (toss[card] == 1){
                shuffled.push(right.shift());
            }
        }
        l = shuffled;
    }
    return l
}

var numCards = parseInt(prompt("Enter number of cards in deck: "))
var l = list(numCards)
var numPerformed = parseInt(prompt("Enter number of shuffles to perform on deck: "));
console.log(shuffle(l))

What am I doing wrong? I think this error is caused due to my inexperience with JavaScript syntax.