Sorting array of float point numbers [duplicate]

Question

I have an array of float point numbers:

[ 82.11742562118049, 28.86823689842918, 49.61295450928224, 5.861613903793295 ]

After running sort() on the array I get this:

[ 28.86823689842918, 49.61295450928224, 5.861613903793295, 82.11742562118049 ]

Notice how 5.8... is bigger than 49.6... for JavaScript (Node). Why is that?

How can I correctly sort this numbers?

Use arr.sort(function (a, b) { return a-b; });. As it stands, the values are being sorted alphabetically. "2" comes before "4", which comes before "5", which comes before "8" (the comparison is the first "letter" of each number...until they match, then it compares the next letter, and so on) — Ian
– Ian, Commented Aug 28, 2013 at 19:45
For reference: w3schools.com/jsref/jsref_sort.asp. By default javascript's array sort method sorts alphabetically and ascending. Hence, why you pass in the sort method provided by @Ian — Suvi Vignarajah
– Suvi Vignarajah, Commented Aug 28, 2013 at 19:51
Generally, don't reference w3 schools as they can be incorrect for a wide range of things. — jtromans
– jtromans, Commented Oct 10, 2013 at 13:12

dc5 · Accepted Answer · 2013-08-28 19:57:33Z

60

Pass in a sort function:

[….].sort(function(a,b) { return a - b;});

results:

[5.861613903793295, 28.86823689842918, 49.61295450928224, 82.11742562118049]

From MDN:

If compareFunction is not supplied, elements are sorted by converting them to strings and comparing strings in lexicographic ("dictionary" or "telephone book," not numerical) order.

edited Aug 28, 2013 at 19:57

user2437417

answered Aug 28, 2013 at 19:49

dc5

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3 Comments

zs2020 Over a year ago

parenthesizes don't match.

dc5 Over a year ago

@CrazyTrain - thanks for the edit. thought I was going blind there :)

Travis Heeter Over a year ago

Here's a shorter version if you're into that sort of thing: yourArray.sort( (a,b) => a-b )

Matt Pavelle · Accepted Answer · 2013-08-28 19:52:23Z

6

The built in JS sort function treats everything as strings. Try making your own:

var numbers = new Array ( 82.11742562118049, 28.86823689842918, 49.61295450928224, 5.861613903793295 );

function sortFloat(a,b) { return a - b; }

numbers.sort(sortFloat);

answered Aug 28, 2013 at 19:52

Matt Pavelle

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1 Comment

Björn Roberg Over a year ago

you should use array literal instead. [...], not new Array(...)

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