extjs3 - Add multiple plugins or adding plugin dynamically -

using extjs 3.4

i trying add 2 plugins in grid panel , code snipet goes on this:

var grid = ext.grid.gridpanel({ ... plugins : [plugin1, plugin2], ... }); 

as giving error tried give 1 plugin dynamic below:

var grid = ext.grid.gridpanel({ ... plugins : [plugin1], ... });  grid.plugins.push(plugin2); grid.dolayout(); 

still not working out. please me regarding one.