I have faced with strange sorting result in Javascript for numeric arrays. For example result of sorting [1,2,10,20,100,200]:

> [1, 2, 10, 20, 100, 200].sort()
[ 1, 10, 100, 2, 20, 200 ]

Why it's happening?

It seems what the array sort cannot be used for sorting numeric arrays directly?

I have faced with strange sorting result in Javascript for numeric arrays. For example result of sorting [1,2,10,20,100,200]:

> [1, 2, 10, 20, 100, 200].sort()
[ 1, 10, 100, 2, 20, 200 ]

Why it's happening?

It seems what the array sort cannot be used for sorting numeric arrays directly?

• javascript
• arrays
• sorting

• 1 Yep. That's how it is defined in the specification: es5.github.io/#x15.4.4.11. – Felix Kling Commented Nov 2, 2013 at 8:01
• 1 possible duplicate of sort not working with integers? – darthmaim Commented Nov 2, 2013 at 8:06

5 Answers 5

From the MDN documentation:

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

(or see the relevant part of the EMCAScript specification, hat tip to Felix Kling for digging up the reference)

If you want to do a numeric sort, then pass a pare function:

[1, 2, 10, 20, 100, 200].sort(function (a,b) { return a-b; });

Sorting arrays in JavaScript is done via the method array.sort(). Calling sort() by itself simply sorts the array in alphabetical order, for example:

var array=[40, 6, 300]; 
array.sort();

Array now bees [300,40,6], the function is going to sort only by first number.

In this case to sort write a function:

Array.sort(function(number1, number2){
    return number1-number2;  
}) 

Array now bees [6,40,300].

array.sort only sorts strings. To sort numbers use this:

[1, 2, 10, 20, 100, 200].sort(function(a,b) { return a-b });

Try this for numeric sorting:

[ 1, 10, 100, 2, 20, 200 ].sort(function(a,b){return a-b})

The sort() method calls the String() casting function on every item and then pares the strings to determine the correct order. This occurs even if all items in an array are numbers. Try this way:

function pare(value1, value2) { 
    if (value1 < value2) {
        return -1;
    } else if (value1 > value2) {
        return 1;
    } else {
    return 0; 
    }
}
[ 1, 10, 100, 2, 20, 200 ].sort(pare);