ArkTS既不能使用展开运算符，也不能使用Object的API，如何合并对象

function arrayToMap(arr: Record<string, Object>[]) { // Record<string, Object>[] is more appropriate than Object[] 
  if (!arr || arr.length === 0) { 
    return null; 
  } 
  let map: Record<string, Object> = {}; 
  for (let index = 0; index < arr.length; index++) { 
    const item = arr[index]; 
    if (item) { 
      for (let k of Object.keys(item)) { 
        map[k] = item[k] 
      } 
    } 
  } 
  return map; 
}