practice in creating cocktail sorting

cocktail_sort.js

<script>
var num = [10, 100, 2, 0, 10, 50];
var text = "<ul>" + num;
var startAgain = false;
var temp;
for ( i = 0, i < num.lenght, i++ ){
    for ( j = 0, j < num.lenght-1-i, j++){
        do
        if ( num[j] > num[j+1]){
            startAgain = true;
            temp = num[j];
            num[j] = num[j+1];
            num[j+1] = temp;
            }
text += "</ul>";
document.getElementById("demo").innerHTML = text + "<br>" + num;
</script>