Given a Map how to sort by value and if value matches sort by key Javascript?

Question

Given Map

{
  'i' => 2, 
  'love' => 2, 
  'leetcode' => 1, 
  'coding' => 1
}

I want to,

Sort the Map based on value
if the value matches, sort by key where the word with the lower alphabetical order comes first.

Expected

{
  "i" => 2, 
  "love" => 2, 
  "coding" => 1,
  'leetcode' => 1, 
}

Solution i have tried

let map = new Map();
map.set("i", 2);
map.set("love", 2);
map.set("coding", 1);
map.set("live", 1);

let output = new Map([...map.entries()].sort((a, b) => {
  //if b[0] and a[0] matches sort by  key stuck here
  return b[0] - a[0];
  
}));

console.log(output);

Subtraction works with numbers. For strings, compareFunction should be b[0].localeCompare(a[0]) — adiga
– adiga, Commented Apr 5, 2019 at 8:07
btw, ...map.entries() is the same as just spreading the map ...map. — Nina Scholz
– Nina Scholz, Commented Apr 5, 2019 at 8:09

Pranav C Balan · Accepted Answer · 2019-04-05 08:24:50Z

5

Value is present at index 1 so update the index to 1 for sorting based on value and use String#localeCompare for string comparison.

let map = new Map();
map.set("i", 2);
map.set("love", 2);
map.set("coding", 1);
map.set("live", 1);

// for sorting based on number we need to return the difference
// in case those are equals difference would be 0(falsy value)
// and the or part will be executed and returns(string comaprison)
let output = new Map([...map].sort((a,b) => b[1] - a[1] || a[0].localeCompare(b[0]) ));

console.log(...output);

or with ES6 Destructuring assignment.

let map = new Map();
map.set("i", 2);
map.set("love", 2);
map.set("coding", 1);
map.set("live", 1);

let output = new Map([...map].sort( ([k1, v1], [k2, v2]) => v2 - v1 || k1.localeCompare(k2) ));

console.log(...output);

FYI : To get a basic idea of how Logical operators refer to MDN docs.

edited Apr 5, 2019 at 8:24

answered Apr 5, 2019 at 8:11

Pranav C Balan

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3 Comments

Rahul Singh Over a year ago

Can you also please explain it will be great rather than just the answer

Pranav C Balan Over a year ago

@RahulSingh : added some basic explanation

Rahul Singh Over a year ago

yes those two lines made me accept the ans over @Nina

Nina Scholz · Accepted Answer · 2019-04-05 08:23:57Z

3

You need to sort the count descending and the string with String#localeCompare ascending.

The first part takes a delta of the two values and while Array#sort is expecting a value

smaller than zero for then a is smaller then b, which means both have the right order, like 1 - 2 where you get -1,
equal zero, that means bot elements have the same value, like 7 - 7, or
greater than zero, which means both elements have to swap, like 5 - 3.

The same result returns localeCompare with strings.

let map = new Map();
map.set("coding", 1);
map.set("love", 2);
map.set("live", 1);
map.set("i", 2);

let output = new Map([...map].sort((a, b) => b[1] - a[1] || a[0].localeCompare(b[0])));

console.log([...output]);

edited Apr 5, 2019 at 8:23

answered Apr 5, 2019 at 8:06

Nina Scholz

388k26 gold badges367 silver badges417 bronze badges

3 Comments

adiga Over a year ago

Sort the Map based on value and if value matches sort by key So, b[1] -a[1] || a[0].localeCompare(b[0])

Rahul Singh Over a year ago

@Nina i guess you missed it , this only compares the string keys not the values and if values matches then you compare keys

Rahul Singh Over a year ago

Can you also please explain it will be great rather than just the answer

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