How to sort array of numbers that includes negative values using localecompare?

Question

I am trying to sort an array from lowest to highest value.

the example below shows it already sorted in this manner

var array = ["-394","-275","-156","-37","82","201","320","439","558","677","796"];

However when I do this:

var array = ["-394", "-275", "-156", "-37", "82", "201", "320", "439", "558", "677", "796"];
array.sort(function(a, b) {
  return a.localeCompare(b, undefined, {
    numeric: true
  })
});
console.log(array);

This is returned (i'm not sure what sorting has occurred):

["-37", "-156", "-275", "-394", "82", "201", "320", "439", "558", "677", "796"]

I've looked at:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/localeCompare

but it doesn't seem to mentioned anything specifically about handling negative numbers.

What is the correct way to sort an array of numbers that includes negative values?

CertainPerformance · Accepted Answer · 2019-07-02 04:05:59Z

7

Because your array items can be coerced to numbers directly, why not do that instead?

var array = ["-394","-275","-156","-37","82","201","320","439","558","677","796"];
array.sort(function(a,b) { return a - b } );
console.log(array);

The a - b, which uses the subtraction operator, will coerce the expressions on both sides to numbers.

Numeric collation unfortunately does not take into account - signs. Your current code results in the sorter sorting - numbers before the numbers without - before them (because - comes before numbers, lexiographically).

console.log('-'.charCodeAt());
console.log('0'.charCodeAt());

So with

  "-37",
  "-156",
  "-275",
  "-394",

37 comes before 156, which comes before 275, which comes before 394. (The same thing is happening with the positive numbers, they just all come afterwards).

edited Jul 2, 2019 at 4:05

answered Jul 2, 2019 at 3:58

CertainPerformance

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1 Comment

user1063287 Over a year ago

interestingly i was actually trying to find "the value closeset to zero" (the negative value closest to zero in this case) in the array (the localeCompare step was just one step in that process), so the "unexpected sorting" that results from "doing it the wrong way" seems to provide a way for me to get the desired value by referencing the first value of the "incorrectly" sorted array. the lexicographic sorting seems to put the value closest to zero (including negative values) at the beginning of the array. i'm sure there is a better way of doing that, but still good to know.

Jack Bashford · Accepted Answer · 2019-07-02 03:59:51Z

0

Just use sort - all your items can be implicitly converted to numbers.

var array = ["-394","-275","-156","-37","82","201","320","439","558","677","796"];
const res = array.sort((a, b) => a - b);
console.log(res);

.as-console-wrapper { max-height: 100% !important; top: auto; }

answered Jul 2, 2019 at 3:59

Jack Bashford

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