unique element in array objects

HTML

<div id="output">Output</div>

JavaScript

function ArrayUtil() {}

ArrayUtil.unique = function (arr) {
    var hash = {}, result = [];
    for ( var i = 0, l = arr.length; i < l; ++i ) {
        //it works with objects! in FF, at least
        if ( !hash.hasOwnProperty(arr[i]) ) { 
            hash[ arr[i] ] = true;
            result.push(arr[i]);
        }
    }
    return result;
}; //function ArrayUtil.unique(arr)

ArrayUtil.pointsArrayToString = function(points) {
	var pointsString, pointsIt;
	pointsString = '[';
	pointsIt = 0;
	_.each(points, function(point) {
		pointsString += ArrayUtil.coordinatesToString(point);
		if( pointsIt < (points.length - 1) ) {
			pointsString += ', ';
		}
		pointsIt++;
	});
	pointsString += ']';
	return pointsString;
};

ArrayUtil.coordinatesToString = function(coordinates) {
	return '[' + coordinates[0] + ',' + coordinates[1] + ']';
};

var dupArray = [[2,3], [2,4], [2,5], [2,5], [2,6], [2,7], [2,4], [2,5], [2,6]];
var uniqArray = ArrayUtil.unique(dupArray);
var output = document.getElementById('output');
output.innerHTML = ArrayUtil.pointsArrayToString(uniqArray);