javascript - Sort JSON string by attribute in JavaScript

Question

I am new to JavaScript and I'm doing some basic exercises. in my code I have a JSON saved in a String. I want to sort it by age attribute, and show the older employee first in my table, by default.

var employees = '{"employees":[ {"name":"Lucas","surname":"White", "email":"[e-mail]", "age":31, "work":{"Company":"userCompany", "role":"userRole"}, "car":[ {"brand":"userCar", "model":"userCar", "year":"userCar", "bollo":"userCar"}, ]},

{"name":"Mary","surname":"userSurname", "email":"[e-mail]", "age":29, "work":{"Company":"userCompany", "role":"userRole"}, "car":[ {"brand":"userCar", "model":"userCar", "year":"userCar", "bollo":"userCar"} ]}, ]}'

I thought about parsing the JSON employees into an object, in order to use the JS methods to compare its values, but I don't think I have the right answer yet.

function compare(a,b) {
    const obj = JSON.parse(employees);
  if ( a.age < b.age ){
    return -1;
  }
  else if ( a.age > b.age ){
    return 1;
  } else {
  return 0;}
  var compared = obj.compare();
  console.log(compared);
}

or...

function sortByAge(a,b){
    const obj = JSON.parse(employees);
    for(var i = 0; i < obj.employees.length; i++){
        return parseInt (a.age) - parseInt (b.age); 
}
var sortedByAge = obj.sortByAge();
console.log(sortedByAge);
}

Is there something I'm missing? Thank you.

标签： javascriptarraysjsonfunctionsorting

Answer 1

不要混合东西。写一个比较器函数：

function byAge(a,b) {
  if (a.age < b.age) return -1;
  else if (a.age > b.age) return 1;
  else return 0;
}

解析 JSON

const obj = JSON.parse(employees);

解决

obj.employees.sort(byAge);
console.log(obj);

---

奖励：通用比较器

function by(property) {
  return function (a, b) {
    if (a[property] < b[property]) return -1;
    else if (a[property] > b[property]) return 1;
    else return 0;
  };
}

const obj = JSON.parse(employees);
obj.employees.sort(by('age'));
console.log(obj);

---

Bonus #2 按数值排序的简写：

function byAge(a, b) {
  return a.age - b.age;
}

之所以有效，是因为计算自然会产生小于 0、大于 0 或正好为零的值，就像if/ else if/else一样。

// even shorter as am arrow function
obj.employees.sort((a, b) => a.age - b.age);