var a = ["A", "B", "C", "D"], j = permute(a);
document.write(
    "<h2>", a.join(" - "), " = ", j.length, "</h2>",
    j.join("<br />")
);

//+ Jonas Raoni Soares Silva
//@ http://jsfromhell.com/array/permute [v1.0]

permute = function(v, m){ //v1.0
    for(var p = -1, j, k, f, r, l = v.length, q = 1, i = l + 1; --i; q *= i);
    for(x = [new Array(l), new Array(l), new Array(l), new Array(l)], j = q, k = l + 1, i = -1;
        ++i < l; x[2][i] = i, x[1][i] = x[0][i] = j /= --k);
    for(r = new Array(q); ++p < q;)
        for(r[p] = new Array(l), i = -1; ++i < l; !--x[1][i] && (x[1][i] = x[0][i],
            x[2][i] = (x[2][i] + 1) % l), r[p][i] = m ? x[3][i] : v[x[3][i]])
            for(x[3][i] = x[2][i], f = 0; !f; f = !f)
                for(j = i; j; x[3][--j] == x[2][i] && (x[3][i] = x[2][i] = (x[2][i] + 1) % l, f = 1));
    return r;
};

//+ Jonas Raoni Soares Silva
//@ http://jsfromhell.com/array/permute [v1.0]

permute = function( v, m ){
	for( var j, l = v.length, i = ( 1 << l ) - 1, r = new Array( i ); i; )
		for( r[--i] = [], j = l; j; i + 1 & 1 << --j && ( r[i].push( m ? j : v[j] ) ) );
	return r;
};

document.write( permute( ["A", "B", "C" ], 1 ).join( "<br />" ), "<hr />" );
document.write( permute( ["A", "B", "C" ], 0 ).join( "<br />" ) );