How to sort an array of integers correctly

Question

Trying to get the highest and lowest value from an array that I know will contain only integers seems to be harder than I thought.

var numArray = [140000, 104, 99];
numArray = numArray.sort();
alert(numArray)

I'd expect this to show 99, 104, 140000. Instead it shows 104, 140000, 99. So it seems the sort is handling the values as strings.

Is there a way to get the sort function to actually sort on integer value?

Answer 1

The question has already been answered, the shortest way is to use sort() method. But if you're searching for more ways to sort your array of numbers, and you also love cycles, check the following

Insertion sort

Ascending:

var numArray = [140000, 104, 99];
for (var i = 0; i < numArray.length; i++) {
    var target = numArray[i];
    for (var j = i - 1; j >= 0 && (numArray[j] > target); j--) {
        numArray[j+1] = numArray[j];
    }
    numArray[j+1] = target
}
console.log(numArray);

Descending:

var numArray = [140000, 104, 99];
for (var i = 0; i < numArray.length; i++) {
    var target = numArray[i];
    for (var j = i - 1; j >= 0 && (numArray[j] < target); j--) {
        numArray[j+1] = numArray[j];
    }
    numArray[j+1] = target
}
console.log(numArray);

Selection sort:

Ascending:

var numArray = [140000, 104, 99];
for (var i = 0; i < numArray.length - 1; i++) {
    var min = i;
    for (var j = i + 1; j < numArray.length; j++) {
        if (numArray[j] < numArray[min]) {
            min = j;
        }
    }
    if (min != i) {
        var target = numArray[i];
        numArray[i] = numArray[min];
        numArray[min] = target;
    }
}
console.log(numArray);

Descending:

var numArray = [140000, 104, 99];
for (var i = 0; i < numArray.length - 1; i++) {
    var min = i;
    for (var j = i + 1; j < numArray.length; j++) {
        if (numArray[j] > numArray[min]) {
            min = j;
        }
    }
    if (min != i) {
        var target = numArray[i];
        numArray[i] = numArray[min];
        numArray[min] = target;
    }
}
console.log(numArray);

Have fun

Answer 2

In the new ES6 world its much easier to do a sort

numArray.sort((a,b) => a-b);

Thats all you need :)

Answer 3

The reason why the sort function behaves so weird

From the documentation:

[...] the array is sorted according to each character's Unicode code point value, according to the string conversion of each element.

If you print the unicode point values of the array then it will get clear.

console.log("140000".charCodeAt(0));
console.log("104".charCodeAt(0));
console.log("99".charCodeAt(0));

//Note that we only look at the first index of the number "charCodeAt(  0  )"

This returns: "49, 49, 57".

49 (unicode value of first number at 140000)
49 (unicode value of first number at 104)
57 (unicode value of first number at 99)

Now, because 140000 and 104 returned the same values (49) it cuts the first index and checks again:

console.log("40000".charCodeAt(0));
console.log("04".charCodeAt(0));

//Note that we only look at the first index of the number "charCodeAt(  0  )"

52 (unicode value of first number at 40000)
40 (unicode value of first number at 04)

If we sort this, then we will get:

40 (unicode value of first number at 04)
52 (unicode value of first number at 40000)

so 104 comes before 140000.

So the final result will be:

var numArray = [140000, 104, 99];
numArray = numArray.sort();
console.log(numArray)

104, 140000, 99

Conclusion:

sort() does sorting by only looking at the first index of the numbers. sort() does not care if a whole number is bigger than another, it compares the value of the unicode of the digits, and if there are two equal unicode values, then it checks if there is a next digit and compares it as well.

To sort correctly, you have to pass a compare function to sort() like explained here.

Answer 4

Array.prototype.sort() is the go to method for sorting arrays, but there are a couple of issues we need to be aware of.

The sorting order is by default lexicographic and not numeric regardless of the types of values in the array. Even if the array is all numbers, all values will be converted to string and sorted lexicographically.

So should we need to customize the sort() and reverse() method like below.

Referred URL

For sorting numbers inside the array

numArray.sort(function(a, b)
{
    return a - b;
});

For reversing numbers inside the array

numArray.sort(function(a, b)
{
    return b - a;
});

Referred URL

Answer 5

By default, the sort method sorts elements alphabetically. To sort numerically just add a new method which handles numeric sorts (sortNumber, shown below) -

    function sortNumber(a,b) {
        return a - b;
    }
    
    var numArray = [140000, 104, 99];
    numArray.sort(sortNumber);
    alert(numArray.join(","));

EDIT: using ES6 arrow functions:

numArray.sort((a, b) => a - b); // For ascending sort
numArray.sort((a, b) => b - a); // For descending sort

Answer 6

Update! Scroll to bottom of answer for smartSort prop additive that gives even more fun!
Sorts arrays of anything!

My personal favorite form of this function allows for a param for Ascending, or Descending:

function intArraySort(c, a) {
    function d(a, b) { return b - a; }
    "string" == typeof a && a.toLowerCase();
    switch (a) {
        default: return c.sort(function(a, b) { return a - b; });
        case 1:
                case "d":
                case "dc":
                case "desc":
                return c.sort(d)
    }
};

Usage as simple as:

var ara = function getArray() {
        var a = Math.floor(Math.random()*50)+1, b = [];
        for (i=0;i<=a;i++) b.push(Math.floor(Math.random()*50)+1);
        return b;
    }();

//    Ascending
intArraySort(ara);
console.log(ara);

//    Descending
intArraySort(ara, 1);
console.log(ara);

//    Ascending
intArraySort(ara, 'a');
console.log(ara);

//    Descending
intArraySort(ara, 'dc');
console.log(ara);

//    Ascending
intArraySort(ara, 'asc');
console.log(ara);

jsFiddle

---

Or Code Snippet Example Here!

function intArraySort(c, a) {
	function d(a, b) { return b - a }
	"string" == typeof a && a.toLowerCase();
	switch (a) {
		default: return c.sort(function(a, b) { return a - b });
		case 1:
		case "d":
		case "dc":
		case "desc":
		return c.sort(d)
	}
};

function tableExample() {
	var d = function() {
			var a = Math.floor(50 * Math.random()) + 1,
				b = [];
			for (i = 0; i <= a; i++) b.push(Math.floor(50 * Math.random()) + 1);
			return b
		},
		a = function(a) {
			var b = $("<tr/>"),
				c = $("<th/>").prependTo(b);
			$("<td/>", {
				text: intArraySort(d(), a).join(", ")
			}).appendTo(b);
			switch (a) {
				case 1:
				case "d":
				case "dc":
				case "desc":
					c.addClass("desc").text("Descending");
					break;
				default:
					c.addClass("asc").text("Ascending")
			}
			return b
		};
	return $("tbody").empty().append(a(), a(1), a(), a(1), a(), a(1), a(), a(1), a(), a(1), a(), a(1))
};

tableExample();

table { border-collapse: collapse; }
th, td { border: 1px solid; padding: .25em .5em; vertical-align: top; }
.asc { color: red; }
.desc { color: blue }

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<table><tbody></tbody></table>

---

.smartSort('asc' | 'desc')

Now have even more fun with a sorting method that sorts an array full of multiple items! Doesn't currently cover "associative" (aka, string keys), but it does cover about every type of value! Not only will it sort the multiple values asc or desc accordingly, but it will also maintain constant "position" of "groups" of values. In other words; ints are always first, then come strings, then arrays (yes, i'm making this multidimensional!), then Objects (unfiltered, element, date), & finally undefineds and nulls!

"Why?" you ask. Why not!

Now comes in 2 flavors! The first of which requires newer browsers as it uses Object.defineProperty to add the method to the Array.protoype Object. This allows for ease of natural use, such as: myArray.smartSort('a'). If you need to implement for older browsers, or you simply don't like modifying native Objects, scroll down to Method Only version.

/* begin */
/* KEY NOTE! Requires EcmaScript 5.1 (not compatible with older browsers) */
;;(function(){if(Object.defineProperty&&!Array.prototype.smartSort){var h=function(a,b){if(null==a||void 0==a)return 1;if(null==b||void 0==b)return-1;var c=typeof a,e=c+typeof b;if(/^numbernumber$/ig.test(e))return a-b;if(/^stringstring$/ig.test(e))return a>b;if(/(string|number){2}/ig.test(e))return/string/i.test(c)?1:-1;if(/number/ig.test(e)&&/object/ig.test(e)||/string/ig.test(e)&&/object/ig.test(e))return/object/i.test(c)?1:-1;if(/^objectobject$/ig.test(e)){a instanceof Array&&a.smartSort("a");b instanceof Array&&b.smartSort("a");if(a instanceof Date&&b instanceof Date)return a-b;if(a instanceof Array&&b instanceof Array){var e=Object.keys(a),g=Object.keys(b),e=e.concat(g).smartSort("a"),d;for(d in e)if(c=e[d],a[c]!=b[c])return d=[a[c],b[c]].smartSort("a"),a[c]==d[0]?-1:1;var f=[a[Object.keys(a)[0]],b[Object.keys(b)[0]]].smartSort("a");return a[Object.keys(a)[0]]==f[0]?-1:1}if(a instanceof Element&&b instanceof Element){if(a.tagName==b.tagName)return e=[a.id,b.id].smartSort("a"),a.id==e[0]?1:-1;e=[a.tagName, b.tagName].smartSort("a");return a.tagName==e[0]?1:-1}if(a instanceof Date||b instanceof Date)return a instanceof Date?1:-1;if(a instanceof Array||b instanceof Array)return a instanceof Array?-1:1;e=Object.keys(a);g=Object.keys(b);e.concat(g).smartSort("a");for(c=0;20>c;c++){d=e[c];f=g[c];if(a.hasOwnProperty(d)&&b.hasOwnProperty(f)){if(a[d]instanceof Element&&b[f]instanceof Element){if(a[d].tagName==b[f].tagName)return c=[a[d].id,b[f].id].smartSort("a"),a[d].id==c[0]?-1:1;c=[a[d].tagName,b[f].tagName].smartSort("d"); return a[d].tagName==c[0]?1:-1}if(a[d]instanceof Element||b[f]instanceof Element)return a[d]instanceof Element?1:-1;if(a[d]!=b[f])return c=[a[d],b[f]].smartSort("a"),a[d]==c[0]?-1:1}if(a.hasOwnProperty(d)&&a[d]instanceof Element)return 1;if(b.hasOwnProperty(f)&&b[f]instanceof Element||!a.hasOwnProperty(d))return-1;if(!b.hasOwnProperty(d))return 1}c=[a[Object.keys(a)[0]],b[Object.keys(b)[0]]].smartSort("d");return a[Object.keys(a)[0]]==c[0]?-1:1}g=[a,b].sort();return g[0]>g[1]},k=function(a,b){if(null== a||void 0==a)return 1;if(null==b||void 0==b)return-1;var c=typeof a,e=c+typeof b;if(/^numbernumber$/ig.test(e))return b-a;if(/^stringstring$/ig.test(e))return b>a;if(/(string|number){2}/ig.test(e))return/string/i.test(c)?1:-1;if(/number/ig.test(e)&&/object/ig.test(e)||/string/ig.test(e)&&/object/ig.test(e))return/object/i.test(c)?1:-1;if(/^objectobject$/ig.test(e)){a instanceof Array&&a.smartSort("d");b instanceof Array&&b.smartSort("d");if(a instanceof Date&&b instanceof Date)return b-a;if(a instanceof Array&&b instanceof Array){var e=Object.keys(a),g=Object.keys(b),e=e.concat(g).smartSort("a"),d;for(d in e)if(c=e[d],a[c]!=b[c])return d=[a[c],b[c]].smartSort("d"),a[c]==d[0]?-1:1;var f=[a[Object.keys(a)[0]],b[Object.keys(b)[0]]].smartSort("d");return a[Object.keys(a)[0]]==f[0]?-1:1}if(a instanceof Element&&b instanceof Element){if(a.tagName==b.tagName)return e=[a.id,b.id].smartSort("d"),a.id==e[0]?-1:1;e=[a.tagName,b.tagName].smartSort("d");return a.tagName==e[0]?-1:1}if(a instanceof Date||b instanceof Date)return a instanceof Date?1:-1;if(a instanceof Array||b instanceof Array)return a instanceof Array?-1:1;e=Object.keys(a);g=Object.keys(b);e.concat(g).smartSort("a");for(c=0;20>c;c++){d=e[c];f=g[c];if(a.hasOwnProperty(d)&&b.hasOwnProperty(f)){if(a[d]instanceof Element&&b[f]instanceof Element){if(a[d].tagName==b[f].tagName)return c=[a[d].id,b[f].id].smartSort("d"),a[d].id==c[0]?-1:1;c=[a[d].tagName,b[f].tagName].smartSort("d");return a[d].tagName==c[0]?-1:1}if(a[d]instanceof Element||b[f]instanceof Element)return a[d]instanceof Element?1:-1;if(a[d]!=b[f])return c=[a[d],b[f]].smartSort("d"),a[d]==c[0]?-1:1}if(a.hasOwnProperty(d)&&a[d]instanceof Element)return 1;if(b.hasOwnProperty(f)&&b[f]instanceof Element)return-1;if(!a.hasOwnProperty(d))return 1;if(!b.hasOwnProperty(d))return-1}c=[a[Object.keys(a)[0]],b[Object.keys(b)[0]]].smartSort("d");return a[Object.keys(a)[0]]==c[0]?-1:1}g=[a,b].sort();return g[0]<g[1]};Object.defineProperty(Array.prototype,"smartSort",{value:function(){return arguments&& (!arguments.length||1==arguments.length&&/^a([sc]{2})?$|^d([esc]{3})?$/i.test(arguments[0]))?this.sort(!arguments.length||/^a([sc]{2})?$/i.test(arguments[0])?h:k):this.sort()}})}})();
/* end */

jsFiddle Array.prototype.smartSort('asc|desc')

---

Use is simple! First make some crazy array like:

window.z = [ 'one', undefined, $('<span />'), 'two', null, 2, $('<div />', { id: 'Thing' }), $('<div />'), 4, $('<header />') ];
z.push(new Date('1/01/2011'));
z.push('three');
z.push(undefined);
z.push([ 'one', 'three', 'four' ]);
z.push([ 'one', 'three', 'five' ]);
z.push({ a: 'a', b: 'b' });
z.push({ name: 'bob', value: 'bill' });
z.push(new Date());
z.push({ john: 'jill', jack: 'june' });
z.push([ 'abc', 'def', [ 'abc', 'def', 'cba' ], [ 'cba', 'def', 'bca' ], 'cba' ]);
z.push([ 'cba', 'def', 'bca' ]);
z.push({ a: 'a', b: 'b', c: 'c' });
z.push({ a: 'a', b: 'b', c: 'd' });

Then simply sort it!

z.smartSort('asc'); // Ascending
z.smartSort('desc'); // Descending

---

Method Only

Same as the preceding, except as just a simple method!

/* begin */
/* KEY NOTE! Method `smartSort` is appended to native `window` for global use. If you'd prefer a more local scope, simple change `window.smartSort` to `var smartSort` and place inside your class/method */
window.smartSort=function(){if(arguments){var a,b,c;for(c in arguments)arguments[c]instanceof Array&&(a=arguments[c],void 0==b&&(b="a")),"string"==typeof arguments[c]&&(b=/^a([sc]{2})?$/i.test(arguments[c])?"a":"d");if(a instanceof Array)return a.sort("a"==b?smartSort.asc:smartSort.desc)}return this.sort()};smartSort.asc=function(a,b){if(null==a||void 0==a)return 1;if(null==b||void 0==b)return-1;var c=typeof a,e=c+typeof b;if(/^numbernumber$/ig.test(e))return a-b;if(/^stringstring$/ig.test(e))return a> b;if(/(string|number){2}/ig.test(e))return/string/i.test(c)?1:-1;if(/number/ig.test(e)&&/object/ig.test(e)||/string/ig.test(e)&&/object/ig.test(e))return/object/i.test(c)?1:-1;if(/^objectobject$/ig.test(e)){a instanceof Array&&a.sort(smartSort.asc);b instanceof Array&&b.sort(smartSort.asc);if(a instanceof Date&&b instanceof Date)return a-b;if(a instanceof Array&&b instanceof Array){var e=Object.keys(a),g=Object.keys(b),e=smartSort(e.concat(g),"a"),d;for(d in e)if(c=e[d],a[c]!=b[c])return d=smartSort([a[c], b[c]],"a"),a[c]==d[0]?-1:1;var f=smartSort([a[Object.keys(a)[0]],b[Object.keys(b)[0]]],"a");return a[Object.keys(a)[0]]==f[0]?-1:1}if(a instanceof Element&&b instanceof Element){if(a.tagName==b.tagName)return e=smartSort([a.id,b.id],"a"),a.id==e[0]?1:-1;e=smartSort([a.tagName,b.tagName],"a");return a.tagName==e[0]?1:-1}if(a instanceof Date||b instanceof Date)return a instanceof Date?1:-1;if(a instanceof Array||b instanceof Array)return a instanceof Array?-1:1;e=Object.keys(a);g=Object.keys(b);smartSort(e.concat(g), "a");for(c=0;20>c;c++){d=e[c];f=g[c];if(a.hasOwnProperty(d)&&b.hasOwnProperty(f)){if(a[d]instanceof Element&&b[f]instanceof Element){if(a[d].tagName==b[f].tagName)return c=smartSort([a[d].id,b[f].id],"a"),a[d].id==c[0]?-1:1;c=smartSort([a[d].tagName,b[f].tagName],"a");return a[d].tagName==c[0]?-1:1}if(a[d]instanceof Element||b[f]instanceof Element)return a[d]instanceof Element?1:-1;if(a[d]!=b[f])return c=smartSort([a[d],b[f]],"a"),a[d]==c[0]?-1:1}if(a.hasOwnProperty(d)&&a[d]instanceof Element)return 1; if(b.hasOwnProperty(f)&&b[f]instanceof Element||!a.hasOwnProperty(d))return-1;if(!b.hasOwnProperty(d))return 1}c=smartSort([a[Object.keys(a)[0]],b[Object.keys(b)[0]]],"a");return a[Object.keys(a)[0]]==c[0]?1:-1}g=[a,b].sort();return g[0]>g[1]};smartSort.desc=function(a,b){if(null==a||void 0==a)return 1;if(null==b||void 0==b)return-1;var c=typeof a,e=c+typeof b;if(/^numbernumber$/ig.test(e))return b-a;if(/^stringstring$/ig.test(e))return b>a;if(/(string|number){2}/ig.test(e))return/string/i.test(c)? 1:-1;if(/number/ig.test(e)&&/object/ig.test(e)||/string/ig.test(e)&&/object/ig.test(e))return/object/i.test(c)?1:-1;if(/^objectobject$/ig.test(e)){a instanceof Array&&a.sort(smartSort.desc);b instanceof Array&&b.sort(smartSort.desc);if(a instanceof Date&&b instanceof Date)return b-a;if(a instanceof Array&&b instanceof Array){var e=Object.keys(a),g=Object.keys(b),e=smartSort(e.concat(g),"a"),d;for(d in e)if(c=e[d],a[c]!=b[c])return d=smartSort([a[c],b[c]],"d"),a[c]==d[0]?-1:1;var f=smartSort([a[Object.keys(a)[0]], b[Object.keys(b)[0]]],"d");return a[Object.keys(a)[0]]==f[0]?-1:1}if(a instanceof Element&&b instanceof Element){if(a.tagName==b.tagName)return e=smartSort([a.id,b.id],"d"),a.id==e[0]?-1:1;e=smartSort([a.tagName,b.tagName],"d");return a.tagName==e[0]?-1:1}if(a instanceof Date||b instanceof Date)return a instanceof Date?1:-1;if(a instanceof Array||b instanceof Array)return a instanceof Array?-1:1;e=Object.keys(a);g=Object.keys(b);smartSort(e.concat(g),"a");for(c=0;20>c;c++){d=e[c];f=g[c];if(a.hasOwnProperty(d)&& b.hasOwnProperty(f)){if(a[d]instanceof Element&&b[f]instanceof Element){if(a[d].tagName==b[f].tagName)return c=smartSort([a[d].id,b[f].id],"d"),a[d].id==c[0]?-1:1;c=smartSort([a[d].tagName,b[f].tagName],"d");return a[d].tagName==c[0]?-1:1}if(a[d]instanceof Element||b[f]instanceof Element)return a[d]instanceof Element?1:-1;if(a[d]!=b[f])return c=smartSort([a[d],b[f]],"d"),a[d]==c[0]?-1:1}if(a.hasOwnProperty(d)&&a[d]instanceof Element)return 1;if(b.hasOwnProperty(f)&&b[f]instanceof Element)return-1; if(!a.hasOwnProperty(d))return 1;if(!b.hasOwnProperty(d))return-1}c=smartSort([a[Object.keys(a)[0]],b[Object.keys(b)[0]]],"d");return a[Object.keys(a)[0]]==c[0]?-1:1}g=[a,b].sort();return g[0]<g[1]}
/* end */

Use:

z = smartSort(z, 'asc'); // Ascending
z = smartSort(z, 'desc'); // Descending

jsFiddle Method smartSort(Array, "asc|desc")