javascript - 获取对象 ES6 中数组的总数/长度

Question

我正在尝试获取每个数组在其各自对象中的总长度计数...

campus : {
    "mchale": {
        "classes":["ESJ030", "SCI339"], // get the length
        "faculty":["Hardy", "Vikrum"]   // get the length
     },
    "lawerence":{
        "classes":["ENG001"],  // get the length
        "faculty":["Speedman", "Lee", "Lazenhower"] // get the length
     }
}

这是我的:

const arrCount = campus.mchale.classes.length + campus.mchale.faculty.length + campus.lawerence.classes.length ...

是否有更好/更漂亮的方法来检索对象中存在的每个数组的总数？

Answer 1

您可以使用 Object.keys与 map和 reduce收集数组，获取它们的长度，然后对这些值求和:

const data = {
    "mchale": {
        "classes":["ESJ030", "SCI339"], // get the length
        "faculty":["Hardy", "Vikrum"]   // get the length
     },
    "lawerence":{
        "classes":["ENG001"],  // get the length
        "faculty":["Speedman", "Lee", "Lazenhower"] // get the length
     }
};

const count = Object.keys(data).map(campusName => {
  const campus = data[campusName];
  return Object.keys(campus).map(key => campus[key].length).reduce((p, c) => p + c, 0);
}).reduce((p, c) => p + c, 0);
console.log(count);