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":"email@gmail.com", "age":31, "work":{"Company":"userCompany", "role":"userRole"}, "car":[ {"brand":"userCar", "model":"userCar", "year":"userCar", "bollo":"userCar"}, ]},

{"name":"Mary","surname":"userSurname", "email":"email@gmail.com", "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.

If you do a `return` inside a loop, the loop will exit at the first iteration ! — polypode, Oct 27 '21 at 07:33
You don't need `parseInt`, the age values in your data are already numbers. — Tomalak, Oct 27 '21 at 07:39
Does this answer your question? [Sorting an array of objects by property values](https://stackoverflow.com/questions/979256/sorting-an-array-of-objects-by-property-values) — pilchard, Oct 27 '21 at 15:36

Tomalak · Answer 1 · 2021-10-27T07:44:17.703

Don't mix things. Write a comparator function:

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

parse the JSON

const obj = JSON.parse(employees);

sort it

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

Bonus: Generic comparator

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 Shorthand for sorting by number values:

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

Works because the calculation naturally works out to values smaller than 0, greater than 0, or exactly zero, just like an if/else if/else would.

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

Sort JSON string by attribute in JavaScript

1 Answers1