# Intermediate Algorithm Scripting - Sorted Union using if not in array to push elements in array

Tell us what’s happening:
I have added all the arrays from function calling into b and tried to add only elements in array ar if they aren’t already in ar (like trying to add unique elements as they appear)…it isn’t working for two case …however it is working for three cases.
What can I do ?

``````function uniteUnique(arr) {
//console.log(arr);
let a=Object.values(arguments).slice(1);
let b=[...arr];
for (let i=0;i<a.length;i++){
for(let j=0;j<a[i].length;j++){
b.push(a[i][j])
}
}
console.log(b)
let ar=[];
for(let i=0;i<b.length;i++){
if (b[i] in ar){
continue
}
else{
ar.push(b[i]);
}
}
console.log(ar);

return ar;
}

uniteUnique([1, 3, 2], [5, 2, 1, 4], [2, 1]);
uniteUnique([1, 3, 2], [5, 4], [5, 6]);
uniteUnique([1, 3, 2, 3], [5, 2, 1, 4], [2, 1])
``````

Challenge: Intermediate Algorithm Scripting - Sorted Union

Take a closer look at the `in` operator, it doesn’t seem to actually check if value is in array.
What would you suggest how use to `' in '` properly to check if the element is in array ?
Array have few methods capable to check if specified element is contained in it. `contains` and `indexOf` to mention couple of them.