ExtJS State

Set provider:

Ext.state.Manager.setProvider(new Ext.state.CookieProvider({
  expires: new Date(new Date().getTime() + (1000 * 60 * 60 * 24 * 30))//30 days
}));

Field Example:

{
    xtype: 'textfield',
    fieldLabel: 'Логин',
    name: 'UserName',
    allowBlank: false,
    validateOnBlur: false,
    blankText: 'Введите логин',
    stateful: true,
    stateId: 'UserName',
    stateEvents: ['blur'],
    getState: function () {
        return { value: this.getValue() };
    },
    applyState: function (state) {
        this.setValue(state.value);
    }
}