@deck.gl/core/dist/utils/flatten.js

deck.gl core library

// deck.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors
/**
 * Flattens a nested array into a single level array,
 * or a single value into an array with one value
 * @example flatten([[1, [2]], [3], 4]) => [1, 2, 3, 4]
 * @example flatten(1) => [1]
 * @param array The array to flatten.
 * @param filter= - Optional predicate called on each `value` to
 *   determine if it should be included (pushed onto) the resulting array.
 * @return Returns the new flattened array (new array or `result` if provided)
 */
export function flatten(array, filter = () => true) {
    // Wrap single object in array
    if (!Array.isArray(array)) {
        return filter(array) ? [array] : [];
    }
    // Deep flatten and filter the array
    return flattenArray(array, filter, []);
}
/** Deep flattens an array. Helper to `flatten`, see its parameters */
function flattenArray(array, filter, result) {
    let index = -1;
    while (++index < array.length) {
        const value = array[index];
        if (Array.isArray(value)) {
            flattenArray(value, filter, result);
        }
        else if (filter(value)) {
            result.push(value);
        }
    }
    return result;
}
/** Uses copyWithin to significantly speed up typed array value filling */
export function fillArray({ target, source, start = 0, count = 1 }) {
    const length = source.length;
    const total = count * length;
    let copied = 0;
    for (let i = start; copied < length; copied++) {
        target[i++] = source[copied];
    }
    while (copied < total) {
        // If we have copied less than half, copy everything we got
        // else copy remaining in one operation
        if (copied < total - copied) {
            target.copyWithin(start + copied, start, start + copied);
            copied *= 2;
        }
        else {
            target.copyWithin(start + copied, start, start + total - copied);
            copied = total;
        }
    }
    return target;
}
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