CODEWITHSUNDEEP
javascriptsorting
shanky
shanky

Reputation: 29

How does returning value1 - value2 results in sorting?

How does returning value1 - value2 end up in sorting, rather than returning the integral value that would be the result of mathematical substraction of the two?

var values = [ 213, 16, 2058, 54, 10];
values.sort(function(value1,value2){ return value1 - value2});

Upvotes: 0

Views: 1078

Answers (3)

Madara's Ghost
Madara's Ghost

Reputation: 175007

The .sort() method accepts a function that accepts two parameters (two elements), and returns a number to determine which element should come first. If the number is negative, value2 is bigger. If the number is positive, value1 is bigger. And if the number is equal to 0, both elements are of the same size, and their order doesn't matter.

Therefore, returning value1 - value2 only works in this case because your elements are numbers. You'd have to employ some more sophisticated logic if they were something else.

Upvotes: 4

kmiyashiro
kmiyashiro

Reputation: 2249

Syntax: [1,2,3].sort(compareFunction), compareFunction is called with two elements from the array at a time.

  • If compareFunction(a, b) returns a negative number, a comes before b.
  • If compareFunction(a, b) returns 0, they are equal and the two elements do not move.
  • If compareFunction(a, b) returns a positive number, b comes before a.

See more examples and detailed documentation at MDN:

Array.prototype.sort: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort

Upvotes: 2

Amadan
Amadan

Reputation: 198436

value1 - value2 is not what's doing the sorting. sort is. However, sort takes a comparator parameter: a function that should return something negative if the first of the two arguments is smaller, 0 if they are equal, and something positive if the first of the two arguments is greater; and value1 - value2 does exactly that, for numeric elements.

Upvotes: 1

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