Get min-max numbers from multidimensional array

Just try with:

var flat = [];
$.map(array, function(item){ $.merge(flat, item); });

// or merge arrays using `join` and `split`

var flat = array.join().split(',');

var max = Math.max.apply( Math, flat ),
    min = Math.min.apply( Math, flat );

Here is pure JS based solution. Without jQuery:

var flattened = [[1, 5, 8, 9], [3, 7], [3, 8, 33], [2], [0, 6]].reduce(function(a, b) {
    return a.concat(b);
});

Math.max.apply(null, flattened) //33

Math.min.apply(null, flattened) // 0

Without jquery, using this answer to add max and min to arrays:

Array.prototype.max = function() {
   return Math.max.apply(null, this);
};

Array.prototype.min = function() {
   return Math.min.apply(null, this);
 };

The answer becomes:

 arr = [[1, 5, 8, 9], [3, 7], [3, 8, 33], [2], [0, 6]]
 maxm = arr.map(function(a){return a.max()}).max();
 minm = arr.map(function(a){return a.min()}).min();