unique array in javascript(which contain all unique values)

how to get a unique array in javascript
=============================

var list1=create_unique_random_array(20,0,19);
var list2=create_unique_random_array(20,0,19);




function create_unique_random_array(num_elements,min,max) {
    var temp, nums = new Array;
    for (var element=0; element<num_elements; element++) {
         while((temp=number_found(random_number(min,max),nums))

 ==-1);
        nums[element] = temp;
    }

    return (nums);
}

function number_found (random_number,number_array) {

    for (var element=0; element<number_array.length; element++) {

        if (random_number==number_array[element]) {
            return (-1);
}
   }

    return (random_number);
}