ExtJS 3 grid autowidth - extjs

Question

In the ExtJS 3, how to set a grid to auto width? I have tried the codes below, it doesn't work.
Thanks
var exceptionGrid = new Ext.grid.GridPanel({
store: exceptionStore,
loadMask: true,
frame: true,
// defaultWidth: 450,
//height: 560,
autoHeight: true,
autoWidth: true,
colModel: new Ext.grid.ColumnModel({
defaults: {
width: 120,
sortable: true
},
columns: [{
header: 'COL1',
dataIndex: 'COL1'
}, {
header: 'COL2',
dataIndex: 'COL2'
}, {
header: 'COL3',
dataIndex: 'COL3'
}, .....]
}),
viewConfig: {
forceFit: false
}
});

Answer 1

From extjs 3 docs:
GridPanel
Notes:
- Although this class inherits many configuration options from base
classes, some of them (such as autoScroll, autoWidth, layout, items,
etc) are not used by this class, and will have no effect.
- A grid requires a width in which to scroll its columns, and a height
in which to scroll its rows. These dimensions can either be set
explicitly through the height and width configuration options or
implicitly set by using the grid as a child item of a Container which
will have a layout manager provide the sizing of its child items (for
example the Container of the Grid may specify layout:'fit').
Grid's width by default takes containers width of course if it was not specified.
Ext.grid.GridPanel#autoExpandColumn will help to expand one column in the grid taking the resting horizontal space. Also will be helpsul to look at Ext.grid.GridView's forceFit and autoFill adjusting widths of columns.

Answer 2

There are Multiple ways to do it based on your design
1.Try width: '100%' and autoHeight:true although autoHeight:true \ height: '100%' creates problem sometime, but width works fine always.
2.Use below code if your grid is the 'only' part of your iframe/web page
var viewport=new Ext.Viewport({
layout: 'fit',
monitorResize : true,
items: [exceptionGrid ]
})
3.If the problem is only with scroll bars,then use
viewConfig: {
forceFit: true
}
4.You can always set the width: window.screen.width - 20 (apply some math around it to make it according to your necessity) and similarly height.