How do I...How to get textfield value in extjs 3.4

try this

Ext.create('Ext.window.Window', {
  bodyPadding: '5 5 5 5',
  items: [
    {
      xtype: 'textfield',
      name: 'firstName',
      emptyText: 'First Name',
      width: 250
    },
    {
      xtype: 'button',
      text: 'click me',
      handler: function() {
        //WAY1
        var value1 = Ext.ComponentQuery.query('textfield[name=firstName]')[0].getValue();
        console.log(value1);

        //WAY2
        var value2 = this.up('window').down('textfield[name=firstName]').getValue();
        console.log(value2);
      }
    }
  ]
}).show();