如何将嵌套对象数组合并为单一数组？使用.reduce()未成功

原始输入数据 #

[
  [
    { jobId: 1, requiredNumber: 1, acceptableRate: 80 },
    { jobId: 2, requiredNumber: 2, acceptableRate: 80 },
    { jobId: 3, requiredNumber: 3, acceptableRate: 80 },
    { jobId: 4, requiredNumber: 1, acceptableRate: 80 }
  ],
  [ { jobId: 2, requiredNumber: 1, acceptableRate: 95 } ],
  null
]

尝试情况与问题 #

使用reduce()方法合并时未成功，得到的输出是多个独立数组和null值：

[
  { jobId: 1, requiredNumber: 1, acceptableRate: 80 },        
  { jobId: 2, requiredNumber: 2, acceptableRate: 80 },        
  { jobId: 3, requiredNumber: 3, acceptableRate: 80 },        
  { jobId: 4, requiredNumber: 1, acceptableRate: 80 }
] [ { jobId: 2, requiredNumber: 1, acceptableRate: 95 } ] null

期望输出 #

希望得到一个包含所有有效对象的单一数组：

[
    { jobId: 1, requiredNumber: 1, acceptableRate: 80 },
    { jobId: 2, requiredNumber: 2, acceptableRate: 80 },
    { jobId: 3, requiredNumber: 3, acceptableRate: 80 },
    { jobId: 4, requiredNumber: 1, acceptableRate: 80 },
    { jobId: 2, requiredNumber: 1, acceptableRate: 95 }
]

正确实现方法 #

方法1：改进reduce()逻辑 #

之前的reduce()未处理null值且合并方式错误，调整后代码如下：

const input = [
  [
    { jobId: 1, requiredNumber: 1, acceptableRate: 80 },
    { jobId: 2, requiredNumber: 2, acceptableRate: 80 },
    { jobId: 3, requiredNumber: 3, acceptableRate: 80 },
    { jobId: 4, requiredNumber: 1, acceptableRate: 80 }
  ],
  [ { jobId: 2, requiredNumber: 1, acceptableRate: 95 } ],
  null
];

const result = input.reduce((acc, current) => {
  // 跳过null元素
  if (current) {
    // 将当前子数组的所有元素推入累加器
    acc.push(...current);
  }
  return acc;
}, []);

console.log(result);

方法2：用flat() + 过滤null #

先过滤掉null，再用flat()展开嵌套数组，简洁高效：

const input = [
  [
    { jobId: 1, requiredNumber: 1, acceptableRate: 80 },
    { jobId: 2, requiredNumber: 2, acceptableRate: 80 },
    { jobId: 3, requiredNumber: 3, acceptableRate: 80 },
    { jobId: 4, requiredNumber: 1, acceptableRate: 80 }
  ],
  [ { jobId: 2, requiredNumber: 1, acceptableRate: 95 } ],
  null
];

const result = input.filter(item => item !== null).flat();

console.log(result);

方法3：用concat() + 扩展运算符 #

过滤null后，通过扩展运算符把所有子数组传给concat()完成合并：

const input = [
  [
    { jobId: 1, requiredNumber: 1, acceptableRate: 80 },
    { jobId: 2, requiredNumber: 2, acceptableRate: 80 },
    { jobId: 3, requiredNumber: 3, acceptableRate: 80 },
    { jobId: 4, requiredNumber: 1, acceptableRate: 80 }
  ],
  [ { jobId: 2, requiredNumber: 1, acceptableRate: 95 } ],
  null
];

const result = [].concat(...input.filter(item => item !== null));

console.log(result);

内容的提问来源于stack exchange，提问作者Mohamed Essam