for little chicken

remove_duplicate_items.js

function removeDuplicatedItem(inputArray) {

    // create a new array to store unique items
    var unduplicatedArray = [inputArray[0]];

    // start looping from 1st item cause we already put the first item into `unduplicatedArray`
    for (let i = 1; i < inputArray.length; i++) {

        // create a flag to store the duplicate status of item
        var existing = false;

        // loop through every item of unduplicatedArray
        for (let j = 0; j < unduplicatedArray.length; j++) {

            // if an item already exists in unduplicatedArray we then set existing = true and stop the loop
            if (inputArray[i] == unduplicatedArray[j]) {
                existing = true;
                break;
            }
        }

        // whenever existing = false we then put the item into unduplicatedArray
        if (!existing) {
            unduplicatedArray.push(inputArray[i]);
        }

        // remember set existing = false for next round
        existing = false;
    }

    return unduplicatedArray;
}

var kq = removeDuplicatedItem([1, 1, 2, 3, 4, 5, 4]);
console.log(kq);