secondary or sub sorting an array in JavaScript

array-sorting-and-sub-sorting.js

// 29 Sep 2017
// 4 Oct 2017 - add name object example.
// 14 Nov 2017 - pass `a.name, b.name` to `byName()`; rename `test` as `diff`.
// 1 Jan 2018 - made some functions more readable.

// Inspired by post at https://alistapart.com/article/what-i-talk-about-when-i-talk-about-sorting
// which covers an example of sorting by age, but does not ensure items of same age are secondarily
// sorted by name in alphabetical order.

// This snippet shows how to do that whether names are strings or objects with first and last properties.

// See also my other array sorting gist:
// https://gist.github.com/dfkaye/2036fb62604b47f80534

var byLastThenFirst = function(a, b) {
  return a.last.localeCompare(b.last) || a.first.localeCompare(b.first);
};

var byName = function(a, b) {
  if (a.last && a.first) {
    return byLastThenFirst(a, b);
  }

  return a.localeCompare(b);
};

var byAge = function(a, b) {
  return (+a) - (+b);
};

var byAgeThenName = function(a, b) {
  return byAge(a.age, b.age) || byName(a.name, b.name);
};

/* name as string */

var flatNames = [
  { name: 'Kei Akamatsu', age: 32 },
  { name: 'Fumiaki Haida', age: 42 },
  { name: 'Tengo Kawana', age: 26 },
  { name: 'Sara Kimoto', age: 11 },
  { name: 'Midori Kobayashi', age: 11 },
  { name: 'Eri Kurono', age: 54 },
  { name: 'Haruki Murakami', age: 6 },
  { name: 'Satoru Nakata', age: 26 },
  { name: 'Yoshio Oumi', age: 26 },
  { name: 'Haruki Oumi', age: 26 },
  { name: 'Miss Saeki', age: 17 },
  { name: 'Yuzuki Shirane', age: 26 },
  { name: 'Kafka Tamura', age: 26 },
  { name: 'Tsukuru Tazaki', age: 32 },
  { name: 'Toru Watanabe', age: 12 }
]

console.log(
  flatNames
    .slice()
    .sort(byAgeThenName)
    .map(function(item) {
      return ''.concat('age: ', item.age, ' name: ', item.name)
    })
    .join('\n')
);

// should see:
/*
age: 6 name: Haruki Murakami
age: 11 name: Midori Kobayashi
age: 11 name: Sara Kimoto
age: 12 name: Toru Watanabe
age: 17 name: Miss Saeki
age: 26 name: Haruki Oumi
age: 26 name: Kafka Tamura
age: 26 name: Satoru Nakata
age: 26 name: Tengo Kawana
age: 26 name: Yoshio Oumi
age: 26 name: Yuzuki Shirane
age: 32 name: Kei Akamatsu
age: 32 name: Tsukuru Tazaki
age: 42 name: Fumiaki Haida
age: 54 name: Eri Kurono
*/

/* name as object */

var nestedNames = [
  { name: { first: 'Kei', last: 'Akamatsu'}, 
    age: 32 },
  { name: { first: 'Fumiaki', last: 'Haida'}, 
    age: 42 },
  { name: { first: 'Tengo', last: 'Kawana'}, 
    age: 26 },
  { name: { first: 'Sara', last: 'Kimoto'}, 
    age: 11 },
  { name: { first: 'Midori', last: 'Kobayashi'}, 
    age: 11 },
  { name: { first: 'Eri', last: 'Kurono'}, 
    age: 54 },
  { name: { first: 'Haruki', last: 'Murakami'}, 
    age: 6 },
  { name: { first: 'Satoru', last: 'Nakata'}, 
    age: 26 },
  { name: { first: 'Yoshio', last: 'Oumi'}, 
    age: 26 },
  { name: { first: 'Haruki', last: 'Oumi'}, 
    age: 26 },      
  { name: { first: 'Miss', last: 'Saeki'}, 
    age: 17 },
  { name: { first: 'Yuzuki', last: 'Shirane'}, 
    age: 26 },
  { name: { first: 'Kafka', last: 'Tamura'}, 
    age: 26 },
  { name: { first: 'Tsukuru', last: 'Tazaki'}, 
    age: 32 },
  { name: { first: 'Toru', last: 'Watanabe'}, 
    age: 12 }
];

console.log(
  nestedNames
    .slice()
    .sort(byAgeThenName)
    .map(function(item) {
      return ''.concat('age: ', item.age, ' name: ', item.name.last, ', ', item.name.first)
    })
    .join('\n')
);

// should see:
/*
age: 6 name: Murakami, Haruki
age: 11 name: Kimoto, Sara
age: 11 name: Kobayashi, Midori
age: 12 name: Watanabe, Toru
age: 17 name: Saeki, Miss
age: 26 name: Kawana, Tengo
age: 26 name: Nakata, Satoru
age: 26 name: Oumi, Haruki
age: 26 name: Oumi, Yoshio
age: 26 name: Shirane, Yuzuki
age: 26 name: Tamura, Kafka
age: 32 name: Akamatsu, Kei
age: 32 name: Tazaki, Tsukuru
age: 42 name: Haida, Fumiaki
age: 54 name: Kurono, Eri
*/