@deck.gl/core/src/utils/deep-merge.ts

deck.gl core library

// deck.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors

/** Merge two viewstates, except `id`
 * For position arrays such as `target`, only override the components that are defined.
 */
export function deepMergeViewState<ViewStateT extends Record<string, any>>(
  a: ViewStateT,
  b: ViewStateT
): ViewStateT {
  const result = {...a};
  for (const key in b) {
    if (key === 'id') continue;
    if (Array.isArray(result[key]) && Array.isArray(b[key])) {
      result[key] = mergeNumericArray(result[key], b[key]) as any;
    } else {
      result[key] = b[key];
    }
  }
  return result;
}

function mergeNumericArray(target: number[], source: number[]): number[] {
  target = target.slice();
  for (let i = 0; i < source.length; i++) {
    const v = source[i];
    if (Number.isFinite(v)) {
      target[i] = v;
    }
  }
  return target;
}