I extend datafield to create monthfield. It will have month picker and display month ( or date - first date of the picked month ).

PHP Code:
Ext.define('Ext.form.field.Month', {
    
extend:'Ext.form.field.Date',
    
alias'widget.monthfield',
    
requires: ['Ext.picker.Month'],
    
alternateClassName: ['Ext.form.MonthField''Ext.form.Month'],
    
selectMonthnull,
    
createPicker: function() {
        var 
me this,
            
format Ext.String.format;
        return 
Ext.create('Ext.picker.Month', {
            
pickerFieldme,
            
ownerCtme.ownerCt,
            
renderTodocument.body,
            
floatingtrue,
            
hiddentrue,
            
focusOnShowtrue,
            
minDateme.minValue,
            
maxDateme.maxValue,
            
disabledDatesREme.disabledDatesRE,
            
disabledDatesTextme.disabledDatesText,
            
disabledDaysme.disabledDays,
            
disabledDaysTextme.disabledDaysText,
            
formatme.format,
            
showTodayme.showToday,
            
startDayme.startDay,
            
minTextformat(me.minTextme.formatDate(me.minValue)),
            
maxTextformat(me.maxTextme.formatDate(me.maxValue)),
            
listeners: { 
        
select:        { scopeme,   fnme.onSelect     }, 
        
monthdblclick: { scopeme,   fnme.onOKClick     },    
        
yeardblclick:  { scopeme,   fnme.onOKClick     },
        
OkClick:       { scopeme,   fnme.onOKClick     },    
        
CancelClick:   { scopeme,   fnme.onCancelClick }        
            },
            
keyNavConfig: {
                
esc: function() {
                    
me.collapse();
                }
            }
        });
    },
    
onCancelClick: function() {
        var 
me this;    
    
me.selectMonth null;
        
me.collapse();
    },
    
onOKClick: function() {
        var 
me this;    
    if( 
me.selectMonth ) {
               
me.setValue(me.selectMonth);
            
me.fireEvent('select'meme.selectMonth);
    }
        
me.collapse();
    },
    
onSelect: function(md) {
        var 
me this;    
    
me.selectMonth = new Date(( d[0]+) +'/1/'+d[1]);
    }
}); 
To use it:
PHP Code:
      xtype'monthfield',
      
format'F, Y',  
      
value: new Date()