i'm using ext js 3.4 and i've the grid with a CheckboxSelectionModel.
I need to verify if the checkbox in the column header (select all) is checked or not.
For Example the below code is my grid:
var xg = Ext.grid;

// shared reader
var reader = new Ext.data.ArrayReader({}, [
{name: 'vis'},
{name: 'company'},
{name: 'price', type: 'float'},
{name: 'change', type: 'float'},
{name: 'pctChange', type: 'float'},
{name: 'lastChange', type: 'date', dateFormat: 'n/j h:ia'},
{name: 'industry'},
{name: 'desc'}

var sm = new Ext.grid.CheckboxSelectionModel({
renderer: function(v, p, record){
if (isDisabled(record)){
return '<div style="display:none;"> </div>';
return '<div class="x-grid3-row-checker" > </div>';
selectAll: function(){
var rowIndex=0;
while(typeof(this.grid.getStore().getAt(rowIndex))!='undefined') {
var record = this.grid.getStore().getAt(rowIndex);
if (isDisabled(record)){
this.grid.getSelectionModel().deselectRow(rowIndex, true);
else {
this.grid.getSelectionModel().selectRow(rowIndex, true);

var grid2 = new xg.GridPanel({
store: new Ext.data.Store({
reader: reader,
data: xg.dummyData
cm: new xg.ColumnModel({
defaults: {
width: 220,
sortable: true
columns: [
{header: "vis", dataIndex: 'vis'},
{id:'company',header: "Company", width: 200, dataIndex: 'company'},
{header: "Price", renderer: Ext.util.Format.usMoney, dataIndex: 'price'},
{header: "Change", dataIndex: 'change'},
{header: "% Change", dataIndex: 'pctChange'},
{header: "Last Updated", width: 135, renderer: Ext.util.Format.dateRenderer('m/d/Y'), dataIndex: 'lastChange'}
sm: sm,
columnLines: true,
title:'Framed with Checkbox Selection and Horizontal Scrolling',
renderTo: document.body,
listeners : {
rowclick : function (in_this, rowIndex, e) {
var record = in_this.getStore().getAt(rowIndex);
if (isDisabled(record)){


// Array data for the grids
Ext.grid.dummyData = [
['1','aaaaaaaaaaaaaa3m Co',71.72,0.02,0.03,'9/1 12:00am', 'Manufacturing'],
['0','Alcoa Inc',29.01,0.42,1.47,'9/1 12:00am', 'Manufacturing'],
['1','Altria Group Inc',83.81,0.28,0.34,'9/1 12:00am', 'Manufacturing'],
['0','American Express Company',52.55,0.01,0.02,'9/1 12:00am', 'Finance'],
['1','American International Group, Inc.',64.13,0.31,0.49,'9/1 12:00am', 'Services'],
['0','AT&T Inc.',31.61,-0.48,-1.54,'9/1 12:00am', 'Services'],
['0','Boeing Co.',75.43,0.53,0.71,'9/1 12:00am', 'Manufacturing'],
['0','Caterpillar Inc.',67.27,0.92,1.39,'9/1 12:00am', 'Services'],
['0','Citigroup, Inc.',49.37,0.02,0.04,'9/1 12:00am', 'Finance'],
['0','E.I. du Pont de Nemours and Company',40.48,0.51,1.28,'9/1 12:00am', 'Manufacturing'],
['0','Exxon Mobil Corp',68.1,-0.43,-0.64,'9/1 12:00am', 'Manufacturing'],
['0','General Electric Company',34.14,-0.08,-0.23,'9/1 12:00am', 'Manufacturing'],
['0','General Motors Corporation',30.27,1.09,3.74,'9/1 12:00am', 'Automotive'],
['0','Hewlett-Packard Co.',36.53,-0.03,-0.08,'9/1 12:00am', 'Computer'],
['0','Honeywell Intl Inc',38.77,0.05,0.13,'9/1 12:00am', 'Manufacturing'],
['0','Intel Corporation',19.88,0.31,1.58,'9/1 12:00am', 'Computer'],
['0','International Business Machines',81.41,0.44,0.54,'9/1 12:00am', 'Computer'],
['0','Johnson & Johnson',64.72,0.06,0.09,'9/1 12:00am', 'Medical'],
['0','JP Morgan & Chase & Co',45.73,0.07,0.15,'9/1 12:00am', 'Finance'],
['0','McDonald\'s Corporation',36.76,0.86,2.40,'9/1 12:00am', 'Food'],
['0','Merck & Co., Inc.',40.96,0.41,1.01,'9/1 12:00am', 'Medical'],
['0','Microsoft Corporation',25.84,0.14,0.54,'9/1 12:00am', 'Computer'],
['0','Pfizer Inc',27.96,0.4,1.45,'9/1 12:00am', 'Services', 'Medical'],
['0','The Coca-Cola Company',45.07,0.26,0.58,'9/1 12:00am', 'Food'],
['0','The Home Depot, Inc.',34.64,0.35,1.02,'9/1 12:00am', 'Retail'],
['0','The Procter & Gamble Company',61.91,0.01,0.02,'9/1 12:00am', 'Manufacturing'],
['0','United Technologies Corporation',63.26,0.55,0.88,'9/1 12:00am', 'Computer'],
['0','Verizon Communications',35.57,0.39,1.11,'9/1 12:00am', 'Services'],
['0','Wal-Mart Stores, Inc.',45.45,0.73,1.63,'9/1 12:00am', 'Retail'],
['0','Walt Disney Company (The) (Holding Company)',29.89,0.24,0.81,'9/1 12:00am', 'Services']