Grow sort an array

array-growsort.md

Growsort

Maak een nieuwe array op basis van een groeisorteeralgoritme, begint bij de oorsprong en groeit vervolgens geleidelijk naar het begin en begin van de array.

Example use case: Loading images for a scroll animation sequence and start loading at a specific percentage

const imagesArray = [
    "image1.jpg",
    "image2.jpg",
    "image3.jpg",
    "image4.jpg",
    "image5.jpg",
    "image6.jpg",
    "image7.jpg",
    "image8.jpg",
    "image9.jpg",
    "image10.jpg",
    "image11.jpg",
    "image12.jpg",
    "image13.jpg",
    "image14.jpg",
    "image15.jpg",
    "image16.jpg",
    "image17.jpg",
    "image18.jpg",
    "image19.jpg",
    "image20.jpg"
];

function growSortIndexes(arr = [], origin = 0) {
    const startIndex = Math.min(origin, Math.max(0, arr.length - 1));
    const indexes = [startIndex];
    for (let offset = 1; offset < arr.length - 1; offset++) {
        if (arr[startIndex + offset]) {
            indexes.push(startIndex + offset);
        }
        if (arr[startIndex - offset]) {
            indexes.push(startIndex - offset);
        }
    }
    return indexes;
}

growSortIndexes(imagesArray, 10); // [10, 11, 9, 12, 8, 13, 7, 14, 6, 15, 5, 16, 4, 17, 3, 18, 2, 19, 1, 0]

function growSort(arr = [], origin = 0) {
    const startIndex = Math.min(origin, Math.max(0, arr.length - 1));
    const indexes = [arr[startIndex]];
    for (let offset = 1; offset < arr.length - 1; offset++) {
        if (arr[startIndex + offset]) {
            indexes.push(arr[startIndex + offset]);
        }
        if (arr[startIndex - offset]) {
            indexes.push(arr[startIndex - offset]);
        }
    }
    return indexes;
}

growSort(imagesArray, 10); // ['image11.jpg', 'image12.jpg', 'image10.jpg', 'image13.jpg', 'image9.jpg', 'image14.jpg', 'image8.jpg', 'image15.jpg', 'image7.jpg', 'image16.jpg', 'image6.jpg', 'image17.jpg', 'image5.jpg', 'image18.jpg', 'image4.jpg', 'image19.jpg', 'image3.jpg', 'image20.jpg', 'image2.jpg', 'image1.jpg']