Is there unique() function in javascript to remove similar elements in array of numbers ?

Question

I have an array of numbers, like: [1, 4, 7, 1, 2, 1, 3, 1, 4].

I would like to remove duplicate elements and sort the result, i.e. the required result is: [1, 2, 3, 4, 7].

Is there any built in Javascript/jQuery functions to do this, or I must write my own ?

Answer 1

No, there's nothing built-in. Also, you need to be aware that the default sort is lexical, so [9, 1, 10].sort() will return [1, 10, 9].

The following will sort and remove duplicates from an array of numbers in place:

function sortAndRemoveDuplicates(arr) {
    arr.sort( function(a, b) { return a - b; } );
    var copy = arr.slice(0);
    arr.length = 0;

    for (var i = 0, len = copy.length; i < len; ++i) {
        if (i == 0 || copy[i] != copy[i - 1]) {
            arr.push(copy[i]);
        }
    }
    return arr;
}

var arr = [1, 4, 7, 1, 2, 1, 3, 10, 1, 4, 10];
sortAndRemoveDuplicates(arr);
console.log(arr); // [1, 2, 3, 4, 7, 10]

Answer 2

The Underscore library is great for all those kinds of tricks; I love it and wouldn't be able to live without it!!

Once you declare it, you call its functions by using the underscore, like this:

_.uniq([1, 4, 7, 1, 2, 1, 3, 1, 4]);
=> [1, 4, 7, 2, 3]

If you want it sorted:

_.uniq([1, 4, 7, 1, 2, 1, 3, 1, 4]).sort();
=> [1, 2, 3, 4, 7]

From the page linked above:

"Underscore provides 60-odd functions that support both the usual functional suspects: map, select, invoke — as well as more specialized helpers: function binding, javascript templating, deep equality testing, and so on."