Random array of numbers without repeating - oojs practice
Your check method is inefficient for large datasets. I'd recommend using a hash instead. This will eliminate the need of iterating over the array every time you want to check if a number is there. 
It is possible for your code to enter an infinite loop if count is greater than max - min. You need to test for this.
The code can be simplified a bit as well.
The recursion slows down the generation dramatically. 


I've take then liberty of performing some optimizations: http://jsfiddle.net/FMSpG/2/

function Randoms(c, l, h) {
    var count = c,
        min = l,
        max = h,
        nums = {},
        out = [],
        r, len = 0;

    if (max - min &lt; count) count = max - min;

    var getRand = function() {
        return Math.floor(Math.random() * (max - min) + min);
    },  check = function(a) {
        return nums[a];
    },  add = function(a) {
        nums[a] = 1;
        out.push(a);
        len++;
    };

    (function init() {
        while (len &lt; count){
            if (len == 0) r = getRand();
            else while (check(r = getRand()));
            add(r);
        }
    })();

    this.get = function() {
        return out;
    };
}


And here's a jsPerf showing the huge difference in performance for large datasets:

http://jsperf.com/unique-randomization